OBSERVATIONAL STUDY OF FINAL CLEANING
AND AHERA CLEARANCE SAMPLING AT
ASBESTOS-ABATEMENT SITES IN NEW JERSEY
by
John R. Kominsky
Ronald W. Freyberg
PEI Associates, Inc.
Cincinnati, Ohio 45246
James A. Brownlee
James H. Lucas, Jr.
Donald R. Gerber
Asbestos Control Service
New Jersey Department of Health
Trenton, New Jersey 08625
EPA Contract No. 68-03-4006
Project Officer
Thomas J. Powers
Water and Hazardous Waste Treatment Research Division
Risk Reduction Engineering Laboratory
Cincinnati, Ohio 45268
RISK REDUCTION ENGINEERING LABORATORY
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
CINCINNATI, OHIO 45268
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DISCLAIMER
The information in this document has been funded wholly or in part by
the U.S. Environmental Protection Agency under Contract 68-03-4006 to PEI
Associates, Inc. It has been subjected to the Agency's peer and administra-
tive review, and it has been approved for publication as an EPA document.
Mention of trade names or commercial products does not constitute endorsement
or recommendation for use.
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FOREWORD
Today's rapidly developing and changing technologies and Industrial
products and practices frequently carry with them the increased generation of
materials that, if improperly dealt with, can threaten both public health and
the environment. The U.S. Environmental Protection Agency (EPA) is charged
by Congress with protecting the Nation's land, air, and water resources.
Under a mandate of national environmental laws, the Agency strives to formu-
late and implement actions leading to a compatible balance between human
activities and the ability of natural systems to support and nurture life.
These laws direct the EPA to perform research to define our environmental
problems, measure the impacts, and search for solutions.
The Risk Reduction Engineering Laboratory is responsible for planning,
implementing, and managing research, development, and demonstration programs
to provide an authoritative, defensible engineering basis in support of the
policies, programs, and regulations of the EPA with respect to drinking
water, wastewater, pesticides, toxic substances, solid and hazardous wastes,
and Superfund-related activities. This publication is one of the products of
that research and provides a vital communication link between the researcher
and the user community.
This report provides information on final cleaning procedures, visual
inspections, and Asbestos Hazard Emergency Response Act (AHERA) clearance
sampling practices observed at 20 asbestos-abatement projects in New Jersey.
It provides matrices that cross-reference case history information on final
cleaning procedures, visual inspection, and AHERA clearance practices at
these sites.
E. Timothy Oppelt, Director
Risk Reduction Engineering Laboratory
ill
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ABSTRACT
A study was conducted during the summer of 1988 to document final clean-
ing procedures and evaluate Asbestos Hazard Emergency Response Act (AHERA)
clearance air-sampling practices used at 20 asbestos-abatement sites in New
Jersey. Each abatement took place in a school building and involved removal
of surfacing material, thermal system insulation, or suspended ceiling tiles.
Final cleaning practices tend to be similar among abatement contractors.
Meticulous attention to detail in cleaning practices is important to a suc-
cessful final cleaning. Sites passing a stringent "no-dust" criterion of a
thorough visual inspection are more likely to pass the AHERA transmission
electron microscopy clearance test. AHERA sampling and analytical require-
ments and recommendations are not completely understood and followed by
consultants conducting clearance air monitoring. Matrices are provided that
cross-reference case history information on final cleaning procedures, visual
inspections, and AHERA clearance practices at these sites.
This report was submitted in fulfillment of Contract No. 68-03-4006 by
PEI Associates, Inc. for the U.S. Environmental Protection Agency's Risk
Reduction Engineering Laboratory. This report covers a period of January
1988 to June 1989 and work was completed as of June 30, 1989.
IV
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CONTENTS
Foreword i i i
Abstract iv
Figures vi
Tables vii
Acknowledgments viii
1. Introduction 1
Background 1
Objectives 1
2. Conclusions and Recommendations 2
Conclusions 2
Recommendations 3
3. Study Design and Methods 4
Site selection 4
Site documentation 4
Airflow and static pressure differential 5
Quality assurance of AHERA clearance data 6
4. Results and Discussion 7
Site descriptions 7
Ventilation and static pressure differentials 7
Final cleaning work procedures and practices 14
Final visual inspection 18
AHERA clearance practices 21
AHERA protocols 21
Observed practices 24
References 34
Appendices
A. Site documentation form of final cleaning procedures
and visual inspections 35
B. Site documentation form of AHERA clearance practices 47
C. Case histories 51
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FIGURES
Page
Airflow performance of HEPA filtration systems 11
Air exchange rates in the abatement area at 20 abatement
sites during final cleaning and AHERA clearance
sampling 12
3 Percentage of 15 sites passing the ACS's visual
inspection for each attempt 20
4 Observed aggressive sweeping times per 1000 square feet
of floor area at 20 asbestos abatement sites 26
5 Recommended and actual number of stationary fans used
during AHERA clearance air monitoring 27
6 Percentage of 18 sites passing AHERA TEM clearance for
each clearance attempt 29
7 Average asbestos concentrations for each AHERA clearance
attempt for the 18 sites cleared by TEM 31
8 AHERA clearance results for sites with individual sample
concentrations greater than 70 s/mm 32
9 Percentage of 15 sites passing AHERA TEM clearance by
total number of ACS visual inspections and AHERA
clearance attempt 33
VI
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TABLES
Page
Site Description for 20 Asbestos-Abatement Projects 8
Abatement Contractors, ASCM Firms, and Analytical
Laboratories Used at the 20 Asbestos Abatement Projects 9
3 Static Pressure Differentials During Final Cleaning and
AHERA Clearance Sampling 13
4 Filter Maintenance Summary at 20 Asbestos-Abatement
Projects 15
5 Final Cleaning Work Practices and Procedures Matrix 16
6 Reasons for Failing NJDOH Visual Inspections at 15
Asbestos-Abatement Projects 22
7 Asbestos Analysis of Bulk Samples Collected by ACS
Inspectors During the Final Visual Inspections 23
8 Clearance Sampling and Analytical Practices Observed at
20 Asbestos-Abatement Sites 25
VII
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ACKNOWLEDGMENTS
This document was prepared for EPA's Office of Research and Development,
Risk Reduction Engineering Laboratory, in fulfillment of Contract No. 68-03-
4006. Thomas J. Powers, P.E., served as the EPA Project Officer and Willian
C. Cain served as the EPA Technical Project Reviewer. The administrative
efforts and support given by Roger Wilmoth of EPA's Office of Research and
Development are greatly appreciated.
Review comments and suggestions provided by William Burch, P.E.; Larry
Longenacker; Kin Wong, Ph.D.; Elizabeth Dutrow; and Joseph Breen, Ph.D., of
EPA's Office of Toxic Substances and William McCarthy, Michael Beard, and
Bruce Hollett, CIH, of EPA's Office of Research and Development are also sin-
cerely appreciated. Jean Chesson, Ph.D., of Chesson Consulting provided peer
review of this report. Christine Hary of Computer Sciences Corporation
prepared the graphics for this report.
John R. Kominsky, C.I.H., and Ronald W. Freyberg of PEI Associates,
Inc., and James A. Brownlee, James H. Lucas, Jr., and Donald R. Gerber of the
Asbestos Control Service, New Jersey Department of Health, were the principal
authors. Robert S. Amick, P.E., of PEI Associates, Inc., served as senior
reviewer. Marty Phillips and Jerry Day of PEI Associates, Inc., performed
the technical edit and copy edit, respectively. The authors gratefully ac-
knowledge the staff of the New Jersey Department of Health, Asbestos Control
Service Field Operations Unit and Technical Unit for their contributions.
viii
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SECTION 1
INTRODUCTION
BACKGROUND
As required under the Asbestos Hazard Emergency Response Act (AHERA) of
1986, the U.S. Environmental Protection Agency (EPA) has issued a final rule
regarding inspections, abatement, and management of asbestos-containing mate-
rials in schools (October 30, 1987; 52 CFR 41826). The final rule specifies
a clearance sampling protocol for determining when an asbestos-abatement site
is clean enough for the critical containment barriers to be removed. It
further specifies the phase-in of transmission electron microscopy (TEM) as
the analytical method to be used on air samples taken for clearance monitor-
ing.
The final cleaning phase of an abatement project is paramount to achiev-
ing a successful abatement as defined in the AHERA final rule. Final clean-
ing applies to the phase of the abatement project that occurs after all
visible asbestos-containing material has been removed from the substrate; the
substrate has been brushed and wet-wiped; a sealant has been applied to the
substrate and to plastic sheeting covering the floors, walls, and fixed
objects to "lock-down" any invisible fibrils that might remain; and all
plastic sheeting (excluding the critical containment barriers) has been
removed. The final cleaning phase of the abatement involves the detailed
cleaning of surfaces in preparation for final visual inspection and AHERA
clearance sampling.
OBJECTIVES
The Risk Reduction Engineering Laboratory (RREL) of the EPA conducted a
study to document final cleaning procedures and practices used at different
asbestos-abatement projects. The study also evaluated AHERA clearance sam-
pling practices used at these abatement sites.
This case history report presents the observations made at 20 asbestos-
abatement projects in New Jersey during the summer of 1988. It includes
matrices that cross-reference case history information on final cleaning
procedures, visual inspections, and AHERA clearance practices at these sites.
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SECTION 2
CONCLUSIONS AND RECOMMENDATIONS
CONCLUSIONS
The following are the principal conclusions reached during this study:
1) Final cleaning practices tend to be similar among abatement con-
tractors. The sequence of cleaning activities depends on the sur-
face from which the asbestos was removed and the physical structure
of the work site. Meticulous attention to detail in cleaning
practices is important to a successful final cleaning.
2) HEPA-filtration units used under normal operating conditions at
asbestos abatement sites tend to perform below the manufacturer's
nominal airflow. The average operating airflow ranged from 50 to
80 percent of the rated nominal airflow for 93 units representing
seven model types.
3) Sites passing a stringent, "no-dust" criterion of a thorough visual
inspection are more likely to pass the AHERA TEM clearance test.
Thirty-three percent of the sites that passed only the Asbestos
Safety Technician (AST) visual inspection, and were not subsequent-
ly inspected by the New Jersey Department of Health (NJDOH), passed
AHERA TEM clearance on the first attempt. Ninety-three percent of
the sites that passed a more thorough visual inspection by the
NJDOH passed AHERA TEM clearance on the first attempt.
4) The initial AHERA Clearance Screening Test requiring an average
asbestos concentration below 70 structures per square millimeter
(s/mm2) is achievable in many cases, thereby eliminating the need
to employ the AHERA Z-test. All 18 sites cleared by TEM passed the
prescreening AHERA TEM clearance criterion of 70 s/mrn2.
5) AHERA sampling and analytical requirements and recommendations are
not completely understood and followed by consultants conducting
clearance air monitoring. The following clearance air sampling and
analytical techniques were observed:
0 Fewer than the required five clearance air samples inside the
abatement area were collected at two sites.
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Improper sampling media was used to collect clearance air
samples, i.e., filter pore size at three sites and filter type
at two sites.
Recommended air sampling flow rates were exceeded at two
sites.
Phase contrast microscopy was improperly used to clear one
site.
Eight of the 20 abatement sites failed to meet the EPA-recom-
mended drying time of 24 hours after completing final cleaning
and before conducting final clearance air monitoring.
Nineteen of the 20 abatement sites used aggressive air sam-
pling techniques. Fourteen of these 19 sites failed to meet
the EPA-recommended aggressive air sweeping rate of at least 5
minutes per 1000 square feet of floor area.
Fifteen of the 20 abatement sites failed to use the number of
circulating fans recommended by AHERA during final clearance
air monitoring. No circulating fans were used at eight of the
sites.
RECOMMENDATIONS
Based on the conclusions outlined above, it is recommended that guidance
documents be developed which address the following topics:
1) Procedures for visual inspections. This study suggests that work
sites passing a stringent visual inspection are less likely to fail
the clearance test and incur the expense of multiple rounds of
sampling and analysis. Guidance for performing a thorough visual
inspection would benefit both the building owner and abatement
contractor.
2) Procedures and protocols of AHERA air monitoring. Improper final
clearance air monitoring resulted partly from a lack of understand-
ing of AHERA air monitoring procedures. The contractors expressed
concern that the EPA-recommended protocols were in different docu-
ments, making it difficult to completely understand the current
protocols. The contractors and AST's recommended that a guidance
document be prepared that contained the procedures and protocols
for proper AHERA clearance air monitoring.
3) Operation of HEPA filtration units. No specific guidance has been
issued regarding the fundamental operating principles of these
units (e.g., decreased airflow performance with increased static
pressure due to filter loading and the addition of manifolds,
flexible ductwork, etc.). Guidance for maximizing the operating
airflow performance of air-filtration units used at asbestos abate-
ment sites is needed.
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SECTION 3
STUDY DESIGN AND METHODS
SITE SELECTION
Although selection of the 20 asbestos-abatement projects was based
largely on availability, each site also met the following criteria:
1) Each abatement project was in a school building.
2) The abatement project involved a) removal of sprayed- or troweled-
on surfacing material; b) removal of thermal system insulation of
mechanical equipment (i.e., boilers, tanks, heat exchangers, pipes,
etc.); or c) removal of suspended ceiling panels.
3) The abatement project was governed by written specifications that
were to comply with the minimum requirements of the State of New
Jersey, Asbestos Hazard Abatement Subcode (N.J.A.C. 5:23-8) and EPA
guidance1 for work practices and procedures to be used in per-
forming asbestos-abatement projects.
4) The abatement project was to be cleared in accordance with the
sampling protocol specified in the AHERA final rule (October 30,
1987; 52 CFR 41826).
SITE DOCUMENTATION
Appendix A contains the site documentation form that was used to docu-
ment the following information for each abatement project:
1) The abatement area's use (classroom, corridor, boiler room, etc.)
and dimensions.
2) The type (acoustical plaster, ceiling panels, pipe insulation,
etc.) and quantity (square feet or linear feet) of asbestos-
containing material (ACM) abated, and type and percentage of
asbestos in the ACM.
3) Final cleaning procedures and work practices.
4) Performance of negative-pressure air filtration systems including
the static pressure differential across critical containment
barriers and the airflow of each air filtration unit.
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5) Results of final visual inspections conducted by the asbestos
safety technician and/or inspector from the Asbestos Control
Service (ACS) of the New Jersey Department of Health, including
reasons why the visual inspection failed.
The background information describing the abatement area, the ACM abat-
ed, and other miscellaneous information was obtained by interviewing at each
site an asbestos safety technician (AST) certified by the New Jersey Depart-
ment of Community Affairs and employed by an Asbestos Safety Control Monitor
(ASCM) firm. The ASCM is employed by the School District or Local Education
Agency. The AST continuously monitors and inspects the asbestos abatement
project in accordance with the Asbestos Hazard Abatement Subcode (N.J.A.C.
5:23-8). The AST must be on the job site continuously during the abatement
project to assure that the work is performed in accordance with the regula-
tions specified in the Asbestos Hazard Abatement Subcode.
Appendix B contains the site documentation form that was used to docu-
ment the AHERA clearance practices used at each site. This information
included:
1) Conditions of sampling, i.e., aggressive versus nonaggressive
sampling, use of fans to maintain air turbulence during clearance
air sampling, etc.
2) Air sampling methods, i.e., filter medium, cassette type, flow
rate, etc.
3) Performance of negative-pressure air filtration systems, including
the static pressure differential across critical containment bar-
riers and the airflow performance of each air filtration unit.
In addition to the information gathered on the site documentation forms
(Appendix A and B), the following three documents were obtained for each
site:
1) Technical specification for the abatement project.
2) The ACS inspector's report on the final visual inspection(s).
3) The AST's project report on the onsite supervision and AHERA clear-
ance air monitoring.
AIRFLOW AND STATIC PRESSURE DIFFERENTIAL
The airflow performance of the air filtration units operating during
both the final cleaning and AHERA clearance phases of the abatement was
measured. The air velocity of the rectangular air-intake face of each air
filtration unit was measured to estimate the airflow performance of the
units. The air-intake face was divided into 16 equal rectangular areas
(Appendix A), and the velocity was measured at the center of each area.2 The
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greatest distance between centers was approximately 6 inches. The air ve-
locity was measured with a calibrated, constant-temperature, thermal anemome-
ter (Kurz Series 440 Air Velocity Meter). This instrument was calibrated
with a National Bureau of Standards (NBS) traceable mass flow meter and
associated equipment. This calibration device is traceable to NBS, Test
Numbers 2.6/167716 A and B and 232.09/209.275.B. The air velocities (feet
per minute) were converted to volumetric flow rate (cubic feet per minute) to
estimate the operating airflow performance of each air filtration unit.
The static pressure differential across the critical containment bar-
riers was measured at each site during both the final cleaning and AHERA
clearance phases of the abatement. Generally, two locations were tested:
one near the decontamination unit and one at a location farthest away from
the decontamination unit. The static pressure differential (inches of water)
was measured with a calibrated, electronic, digital micromanometer (Neotron-
ics Model Type EPM 201).
QUALITY ASSURANCE OF AHERA CLEARANCE DATA
Clearance of each abatement site was based on the analyses of the final
clearance air samples collected by the AST. The analyses were obtained from
the laboratory report contained in the final project report prepared by the
ASCM firm. The analysis of the samples and the corresponding quality control
and quality assurance procedures were specified by the contract with the
performing analytical laboratory to be conducted in accordance with the
requirements in the AHERA final rule.
The conditions of sampling and the sampling procedures used by the AST
were documented for comparison with the requirements specified in the AHERA
final rule. The information was recorded on the site documentation form in
Appendix B.
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SECTION 4
RESULTS AND DISCUSSION
SITE DESCRIPTIONS
Table 1 presents a site description for the 20 asbestos-abatement proj-
ects evaluated. Sixteen of the abatement projects involved general occupancy
areas (classrooms, offices, recreational rooms, corridors, etc.); three
involved boiler rooms and mechanical equipment rooms; and one involved both
types of areas. The ACM abated at 13 of the project sites involved surfacing
material (acoustical plaster or fireproofing), 8 involved thermal system
insulation on mechanical equipment (pipes and boilers), 3 involved both
surfacing material and thermal system insulation, and 2 involved suspended
ceiling tiles. The ACM contained chrysotile asbestos (from 2 to 93 percent)
at 17 projects, amosite asbestos (from 2 to 10 percent) at 2 projects, and
both chrysotile (from 10 to 75 percent) and amosite (from 30 to 40 percent)
at 1 project.
The projects involved 11 abatement contractors, eight ASCM firms, and
five analytical laboratories (Table 2). A single abatement contractor, ASCM
firm, or analytical laboratory was involved in a maximum of 5, 6, or 12
projects, respectively.
VENTILATION AND STATIC PRESSURE DIFFERENTIALS
High-efficiency particulate air (HEPA) filtration systems serve as the
primary engineering control for the removal of asbestos particulate from
airstreams in active abatement areas. The HEPA units draw contaminated air
from the abatement area and exhaust the filtered air to an exterior area,
usually outside the building. This constant exhausting of large volumes of
air from within the abatement area at a rate higher than that of the makeup
air supplied to the abatement area creates a negative-pressure condition
relative to surrounding areas, which ensures that any air leakage is inward.
Current EPA guidance1 on work practices and procedures recommends the
use of enough HEPA-filtration units to remove a volume of air equivalent to
the work area volume at least four times per hour (i.e., four air changes per
hour). This recommended air exchange rate is based on engineering judgment.
Current OSHA regulations require the exhausting of a sufficient amount of air
to create a pressure of -0.02 inch of water within tne abatement area with
respect to the area outside the enclosure.3
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TABLE 1. SITE DESCRIPTION FOR 20 ASBESTOS-ABATEMENT PROJECTS
00
Site
A
B
C
D
E
F
G
H
I
J
K
L
M
N
0
P
Q
R
S
T
a ACM =
f?m*mM<
Type of ACMa
Acoustical plaster
Acoustical plaster
Pipe/boiler Insulation
Acoustical plaster
Boiler insulation
Ceiling panels
Pipe/boiler insulation
Boiler insulation
Acoustical plaster
Pipe insulation
Acoustical plaster
Fireproof ing
Acoustical plaster
Acoustical plaster
Pipe Insulation
Acoustical plaster
Ceiling tiles
Acoustical plaster
Pipe Insulation
Acoustical plaster
Pipe Insulation
Acoustical plaster
Acoustical plaster
Abatement area
General occupancy
General occupancy
General occupancy and
boiler room
Boiler and mechanical
equipment rooms
Boiler room
General occupancy
Boiler room
Boiler room
General occupancy
General occupancy
General occupancy
Mechanical equipment room
General occupancy
General occupancy
General occupancy
General occupancy
General occupancy
General occupancy
General occupancy
General occupancy
General occupancy
General occupancy
General occupancy
Approximate
nij/i n 1 1 t u
ijuoii L. i \,y
Of ACM
19,100 ft2
5,400 ft2
QNSC
QNS
QNS
1,500 ft2
2,200 ft2
QNS
21,000 ftZ
100 ft
5,100 ft2
5,300 ft2
8,200 ft2
1,600 ft2
QNS
11,000 ft2
2,100 ft2
8,500 ft2
1,600 fr
5,400 ft2
2,900 ft
7,200 ft2
4,100 ft2
Type and percent asbestos
Chrysotile Amosite
5 -
2 -
40 -
20 -
40 -
30 -
10 -
25 -
40 -
5 -
10 -
10 -
15 -
40 -
10 -
91 -
24 -
2 -
10 -
10 -
10 -
10
6
60
35
60
2 - 8
40
75 30 - 40
50
60
25
25
25
25
60
25
5-10
93
60
6
25
20
25
Asbestos-containing material.
• 1 1
c QNS = Quantity of ACM not specified.
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TABLE 2. ABATEMENT CONTRACTORS, ASCM FIRMS, AND ANALYTICAL LABORATORIES
USED AT THE 20 ASBESTOS-ABATEMENT PROJECTS
Site
A
B
C
D
E
F
G
K
I
J
K
L
H
N
0
P
Q
R
S
T
Total
Abatement contractor
1
X
X
X
X
X
5
2
X
X
2
3
X
X
X
X
4
4
X
1
5
X
1
6
X
1
7
X
1
8
X
X
2
9
X
1
10
X
1
11
X
1
ASCH firm
1
X
1
2
X
X
2
3
X
X
X
X
X
X
6
4
X
X
X
X
4
5
X
X
2
6
X
1
7
X
X
X
3
8
X
1
Laboratory
1
X
1
2
X
X
X
X
X
X
X
X
X
X
X
X
12
3
X
X
X
X
4
4
X
X
2
5
X
1
VO
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Air-intake volumes for each HEPA-filtration unit in operation during
final cleaning and AHERA clearance sampling were measured at each of the 20
sites in this study. Seven different models were observed and evaluated.
The average operating airflow for each model was compared with the manufac-
turer's nominal airflow, i.e., the manufacturer's advertised rated peak
capacity. Actual average operating airflow ranged from 50 to 80 percent of
the nominal airflow for these models. This reduction in airflow performance
is comparable to another study which showed a 50 to 60 percent reduction in
airflow capacity.** Figure 1 illustrates the actual average operating airflow
as a percentage of nominal airflow for the seven observed models. The re-
duced airflow performance of the filtration units is probably due to the
increased static pressure associated with extended and obstructed exhaust
duct conditions and to increased particulate loadings on the filters. The
significance of this reduced operating flow rate is in the procedure used to
determine the number of air-filtration units necessary to achieve the desired
minimum ventilation rate (i.e., four air changes per hour). Assuming the
air-filtration units are operating at the manufacturer's specified nominal
airflow rate could result in actual ventilation rates significantly below
project design specifications.
Despite the lower-than-assumed ventilation rates of the observed HEPA-
filtration units, enough units were used at all but one site to achieve a
minimum of four air exchanges per hour during AHERA clearance sampling.
Also, only two sites failed to meet the recommended air-exchange rate during
final cleaning. Figure 2 shows the air-exchange rates during final cleaning
and AHERA clearance sampling at each of the sites. Actual air-exchange rates
ranged from 2 to 13 per hour during final cleaning and 3 to 13 per hour
during AHERA clearance sampling.
Static pressure differential across the containment barriers was mea-
sured at one or more test locations at each of the 20 abatement sites during
both final cleaning and AHERA clearance sampling. Eight of the 20 sites
showed an average static pressure differential of at least -0.02 inch of
water during final cleaning. Nine sites showed an average pressure differen-
tial of at least -0.02 inch of water during AHERA clearance sampling. The
average static pressure differential for all sites ranged from -0.03 to
-0.01 inch of water during both final cleaning and AHERA clearance sampling.
Table 3 summarizes the average pressure differentials during final cleaning
and AHERA clearance sampling at each site.
Continuous monitoring of the static pressure differential across the
containment barriers was conducted at only one site. Ventilation smoke tubes
were typically used at the beginning of each work shift at all abatement
sites to verify visually that the containment enclosure remained under nega-
tive pressure (i.e., a noticeable inward movement of air existed through the
decontamination facility).
At all of the observed abatement sites, the HEPA-filtration units were
placed so that the makeup air entered the work area through the personnel
decontamination facility or the waste load-out port. An interconnected
flexible duct was used to vent the exhaust air directly outdoors through
windows in the work area or through windows in areas outside the abatement
10
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Average Percent of Nominal Airflow
100 -i
eo -
40 -
20 -
79%
w
ll
78%
74%
63%
^r
3
66%
51%
61%
mm
mm
6
HEPA Model
Figure 1. Airflow performance of HEPA filtration systems.
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Air Changes Per Hour
Final Cleaning
AHERA Sampling
ABCDEFGHI JKLMNOPQRST
Recommended
Air Exchange
Rate
Figure 2. Air exchange rates in the abatement area at 20 asbestos
abatement sites during final cleaning and AHERA clearance
sampling.
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TABLE 3. STATIC PRESSURE DIFFERENTIALS DURING FINAL
CLEANING AND AHERA CLEARANCE SAMPLING
Site
A
B
C
D
E
F
G
H
I
J
K
L
M
N
0
P
Q
R
S
T
Final cleaning
-0.010
-0.020
-0.010
-0.015
-0.013
-0.020
-0.010
-0.013
-0.023
-0.020
-0.020
-0.010
-0.020
-0.010
-0.020
-0.025
-0.010
-0.015
-0.015
-0.015
AHERA clearance sampling
-0.023
-0.020
-0.015
-0.020
-0.010
-0.020
-0.010
-0.015
-0.023
-0.010
-0.010
-0.010
-0.015
-0.010
-0.020
-0.020
-0.010
-0.020
-0.020
-0.025
13
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area. At five sites, it was noted that torn ductwork passed through areas
outside and adjacent to the work site before being vented outdoors. This
damaged ductwork allowed a percentage of the exhaust air to be distributed to
adjacent building areas, which could have contaminated the perimeter areas of
the abatement site.
Each asbestos-abatement contractor was responsible for maintaining the
HEPA-filtration units. Prefilters, secondary filters, and HEPA filters were
changed periodically during the abatement efforts. Table 4 summarizes the
frequency of filter maintenance on each HEPA-filtration unit during the
abatement activity. Generally, the prefilters and secondary filters were
changed when they became visibly dirty. At several sites, the prefilters
were changed only once a day. The HEPA filters were generally changed either
when an audible alarm was actuated (indicating that minimum air was passing
through the filters) or when a set length of time had elapsed, per manufac-
turer's specifications.
FINAL CLEANING WORK PROCEDURES AND PRACTICES
Upon completion of the abatement process, the work area must be cleaned
in preparation for its restoration to normal use. Various work procedures
and practices are used. The ultimate purpose of each is to ensure that
postabatement concentrations of asbestos fibers are at or below the concen-
trations present before the abatement work began and that they are in com-
pliance with the final clearance requirements under the AHERA final rule.
In this study, final cleaning began at each project site after the
encapsulated plastic sheeting was removed from the walls, floors, and fixed
objects. The critical barriers, windows, doors, and heating, ventilation,
and air-conditioning (HVAC) vents remained sealed. The air-filtration units
remained in service.
Table 5 presents a matrix of the final cleaning procedures and work
practices used at the 20 asbestos-abatement sites. At two abatement sites
(Sites E and J), aggressive cleaning techniques were used. Aggressive clean-
ing involves sweeping the surfaces with the exhaust from a hand-held 1-horse-
power leaf blower to dislodge any residual debris, and then allowing the
airborne particulate to settle. Aggressive cleaning was conducted at Site E
before the site was recleaned after it had failed the first AHERA clearance
attempt; and at Site J after the walls and other surfaces had been sprayed
with water and allowed to dry and hard-to-reach areas such as indented cor-
ners, crevices around doors and windows, etc., had been cleaned with a vacuum
equipped with a HEPA filter.
Final cleaning was organized so the workers at 16 of the sites began in
the areas farthest from the personnel decontamination facility and worked
toward it. The opposite work direction was observed at the remaining four
sites. No association appeared to exist between work direction and the
location of the air-filtration units.
14
-------
TABLE 4. FILTER MAINTENANCE SUMMARY AT 20 ASBESTOS-ABATEMENT PROJECTS
Abatement site
Abatement phase HEPA system maintenance
BCQ inninti of pro met. Chdnocd HE PA f 1 1 tcr
Prior to final Changed pref liter
cleaning
Changed secondary filter
rhannaH UPDA filtor
Lnangeu ntrii 1 1 1 ipr
During abatement Pref liter changed daily
Pret liter changed when
visibly dirty
Secondary filter changed
daily
Secondary filter changed
when visibly dirty
Secondary filter changed
after each workshift
Secondary filter changed
every 48 hours
HEPA filter changed when
alarm activated
HEPA filter changed per manu-
facturer's specifications
A
X
X
X
X
X
X
B
X
X
X
X
X
X
c
X
X
X
X
X
X
D
X
X
X
X
X
X
E
X
X
X
X
X
X
F
X
X
X
X
X
X
G
](
X
X
X
X
X
X
H
X
X
X
X
X
X
I
X
X
X
X
X
X
X
J
X
X
X
X
X
K
X
X
X
X
X
L
X
X
X
X
X
H
X
X
X
X
X
X
N
X
X
X
X
X
0
X
X
X
X
X
X
p
X
X
X
X
X
Q
X
X
X
X
X
R
X
X
X
X
X
s
X
X
X
X
X
T
X
X
X
X
X
-------
TABLE 5. FINAL CLEANING WORK PRACTICES AND PROCEDURES MATRIX
Final cleaning practices and procedures
Worked toward decontamination facility
Worked away from decontamination facility
Aggressive cleaning "air sweeping" surfaces
Spraying of surfaces with amended water
Spraying of surfaces with water
Wire-brushing of abated surfaces
Scraping, brushing ceiling-wall intersections
HEPA- vacuuming of corners, crevices, floor-wall
intersections
Wet-wiping of horizontal and vertical surfaces
0 Cotton rags dampened with amended water
0 Paper bath towels dampened with amended water
° Sponge dampened with amended water
Dry sweeping of floors
Wet mopping of floors with amended water
Removing plastic sheeting from air-filtration
units and associated exhaust ducts
Wet mopping of floors with amended water
a second time
Wet-wiping and/or HEPA- vacuuming of designated
areas based on AST's visual Inspection
Wastewater and disposable cleaning materials
placed in double-layer 6-mil- thick plastic bags
Wet-wiped asbestos-disposal bags before removing
from abatement area
Miscellaneous observations
0 Cleaning water beneath vinyl floor tiles
0 Use of agent to gel wastewater
A
X
1
2
3
4
S
6
X
B
X
1
2
3
4
5
X
X X
C
X
1
2
3
4
X
X
1
X !
D
X
1
2
3
4
5
E
X
X
i !
1
2
3
i
X i X
1
i
: i
Abatement site and sequence of final cleaning8
F
X
1
2
G
X
3
1
2
4
3 5
6
i
,
X X
X X
,
H
X
1
2
3
4
5
X
X
I
X
1
2
3
3
J
X
X
1
2
3
4 4
5 5
x ; x
;
i
X ' X
K
X
1
2
L
X
1
2
3
3 ; 4
5
M
X
1
2
3
4
5
X . X X
1
x
X
; ,
i i
X
•
; i , x !
N
X
2
1
3
4
5
6
0 P
X
2
2
1
3
4
5
6
X
X
X
X
X
1
3
Q
x
3
1
2
4
4 1 5
i
i
1
X X
i
i
X i X
'
.
]
'
R
X
2
3
4
5
6
X
X
S
X
1
2
3
4
5
X
T
X
1
2
3
X
X X
Total
16
4
2
1
11
4
5
16
13
6
1
1
20
4
13
18
20
0
i
I '
i
' x . ! , : 1 2
i !
i
1
CT»
4 Number denotes sequence of final cleaning.
-------
The sequence and nature of the cleaning tasks seemed to depend on the
substrate from which the ACM was removed (e.g., concrete ceiling versus a
T-bar grid system for suspended ceiling tiles) or on the physical structure
(i.e., concrete walls, wood floor in a gymnasium, etc.) of the abatement
area. Final cleaning usually began with the spraying of the walls, plastic
critical containment barriers, and other surfaces with a water mist to remove
any loosely bound debris. The resultant asbestos-containing water on the
floor was gathered into pools by use of a rubber squeegee or (less frequent-
ly) with push-type brooms. The bulk of the pooled water was scooped up with
plastic-bladed shovels. The water was placed in double-layered, 6-mil-thick,
asbestos-disposal bags, which generally contained plastic that had been
removed from the walls and floors or protective clothing that had been used
by the workers. The residual water removed with a wet vacuum was also placed
in the disposal bags. At one site, the wastewater in the disposal bags was
solidified with a gelling compound to minimize the potential for its sub-
sequent release during storage.
At two sites, some of the wash water penetrated the seams between the
floor tiles and caused them to buckle. These buckled floor tiles were
sporadically distributed throughout the abatement areas. At both sites, the
asbestos-containing water beneath the floor tiles was allowed to dry, and the
tiles were not repaired as part of the abatement. These areas could be
potential sources of airborne asbestos fibers when repaired later by mainte-
nance personnel.
Although to a lesser extent than the spraying of surfaces with water,
some final cleaning began with the scraping or brushing of the substrate to
remove any visible debris.
The surfaces, particularly hard-to-reach areas such as indented corners,
crevices around doors and windows, floor-wall junctions, etc., were then
cleaned with a HEPA-filtered vacuum. At several sites, final cleaning began
with the HEPA-vacuuming of surfaces.
The vertical and horizontal surfaces were then wet-wiped with amended
water. The contractors reportedly prepared the amended water solution by
mixing approximately 1 or 2 ounces each of 50 percent polyoxyethlyene ester
and 50 percent polyoxyethylene ether in 5 gallons of water.
The elevated horizontal and vertical surfaces were usually wiped first,
and then all the other surfaces. All the surfaces except the floors were
wiped with cotton rags, paper towels (bath size), or a sponge dampened with
amended water. Several abatement contractors said they did not use cotton
rags or sponges because their repeated use increased the potential for smear-
ing residual particulate on the surfaces being cleaned. Although the paper
towels were sometimes reused, such reuse appeared to be markedly less than
that observed for cotton rags or sponges at other sites. Deterioration
appeared to be the primary factor that prompted a worker to discard a paper
towel. A bucket of amended water was either used by a single worker or
shared by several workers and the same bucket was used for both rinsing and
dampening of the rags or paper towels. The workers did not wipe the surfaces
in any one direction. The cotton rags, paper towels, or sponges were not
17
-------
replaced frequently, especially during the cleaning of elevated and hard-to-
access surfaces. Nor was the amended water changed frequently.
After the walls, windows, and other surfaces had been wet-wiped, the
last step in the final cleaning involved a complete mopping of the floors
with a clean mop head wetted with amended water. The floors were mopped once
at 7 of the sites and twice at 13 of the sites. The mop heads were changed
infrequently. No changes in the water were observed during this procedure at
any of the sites.
Before the floors were mopped a second time at four of the sites, the
plastic sheeting covering the air-filtration units and a plastic sleeve that
covered the associated flexible exhaust ducts were removed. Both coverings
had been installed before abatement work began. According to the contrac-
tors, this practice simplified the cleaning of this equipment, particularly
the flexible exhaust ducts.
At all sites, wastewater from the wet-wiping and mopping operations was
treated as asbestos-containing water and placed in double-layered, 6-mil-
thick, standard asbestos disposal bags. These standard asbestos disposal
bags containing wastewater were not placed in leak-tight containers. The
wastewater in the disposal bags was solidified with a gelling compound at 1
of the 20 abatement sites. The rags, paper towels, sponges, mop heads, and
other materials used during final cleaning were also placed in these bags.
The bags were not generally wet-wiped with amended water before being removed
from the abatement area.
Final cleaning practices tended to be similar among abatement contrac-
tors. The sequence of cleaning activities depended on the surfaces from
which the asbestos was removed and the physical structure of the work site.
Meticulous attention to detail in cleaning practices is important to a suc-
cessful final cleaning.
Upon completing final cleaning, the abatement contractor immediately
requested a final visual inspection by an onsite AST. The AST conducted the
visual inspection within 1 to 2 hours after notification. The AST identified
areas that required further cleaning at 18 of the 20 sites. Further cleaning
typically involved the vacuuming or wet-cleaning of those areas failed by the
AST.
FINAL VISUAL INSPECTION
Final visual inspection involves examining the abatement area for evi-
dence that the remedial actions have been successfully completed, as indicat-
ed by the absence of residue, dust, and debris.1'5 The basic premise of a
final visual inspection is that an area where residue or debris visible to
the unaided eye is still present is not clean enough for clearance air sam-
pling.
18
-------
Final Visual Inspection by AST's
Upon completion of final cleaning, a final visual inspection was con-
ducted at each of the 20 abatement sites by an onsite AST. Two of the 20
sites passed the first visual inspection, and 18 of the 20 sites required and
passed a second visual inspection.
Final Visual Inspection by NJDOH's ACS
The New Jersey Department of Health's Asbestos Control Service (ACS)
conducted final visual inspections at 15 of the 20 abatement projects. These
included Sites A through C, H through I, and K through T. This inspection is
a part of the State's traditional quality assurance program which provides a
check and balance to asbestos abatement, ensuring that high-quality abatement
and state-of-the art work practices are used.
The ACS inspector first visually examined all substrate surfaces to en-
sure that no ACM remained. Special attention was given to pipes, structural
members, ceiling tile grid bars, and irregular surfaces with corners and
hard-to-reach areas. If any quantity of ACM remained, the site failed the
visual inspection and additional removal work was performed before another
visual inspection was conducted.
The ACS inspector then determined if the work site had been adequately
cleaned. All surfaces were examined for dust and debris, especially overhead
areas (such as tops of suspended light fixtures and ventilation ducts) and
areas under stationary fixtures. One or both of the following techniques
were used for examining surfaces to establish that a "no dust" criterion had
been achieved:
1) Using a damp cloth to collect dust from the surface and then in-
specting the cloth for evidence of dust.
2) Darkening the room and shining a flashlight so that the light beam
just glances across any smooth horizontal or vertical surface. A
gloved finger is then run across the illuminated area; if a line is
left on the surface, dust is still present.
If either of these techniques showed that dust still remained, the ACS
inspector recommended recleaning of the work area before its reinspection.
If debris was found, the ACS inspector collected bulk or wipe samples of the
debris and submitted them for analysis by the New Jersey Department of
Health's Public Health and Environmental Laboratories in Trenton, New Jersey.
From one to seven visual inspections were conducted at each abatement
site. Figure 3 shows the percentage of sites that passed the visual inspec-
tion per given attempt. The largest percentage of sites (33.5%) passed the
visual inspection on the second attempt. The cumulative percentages of sites
passing the visual inspection were as follows: 40 percent by the first and
second attempts, 66.7 percent by the third attempt, and 93.4 percent by the
fourth attempt.
19
-------
r\:
O
% Sites Passing Visual Inspection
35-
30 -
25-
20-
15-
10
6.7%
1st
33.3%
2nd
26.7%
26.7%
ill
P
ill
0%
3rd
4th
5th
Visual Inspection
6.7%
0%
6th
7th
Figure 3. Percentage of 15 sites passing the ACS's visual inspection
for each attempt.
-------
Table 6 lists the reasons why sites failed the ACS inspectors' visual
inspections at 15 sites. Fourteen of the 15 sites failed visual inspection
for more than one reason. The most commonly identified reason (cited at 8 of
the 15 sites) was the presence of debris on pipes, pipe fittings, and hang-
ers. The next most common reason was debris on floors, on horizontal surfac-
es, and in wall-penetrations. Table 6 also lists 23 other less commonly
reported reasons for failing the visual inspection.
Table 7 presents the asbestos analysis of 81 bulk samples collected by
the ACS inspectors to determine the asbestos content of debris found during
the visual inspections. Asbestos was present in approximately 90 percent (73
of 81) of these samples.
All 20 abatement sites passed an onsite AST visual inspection according
to each AST requirement. Fifteen of the 20 sites were subsequently inspected
by the NJDOH's ACS inspectors. Only one site passed the first visual inspec-
tion. Observation of inspection practices and procedures showed that the ACS
inspectors conducted a more stringent and thorough visual inspection.
AHERA CLEARANCE PRACTICES
The asbestos abatement industry is halfway into its second year since
the Asbestos Hazard Emergency Response Act (AHERA) Final Rule (40 CFR Part
763) went into full effect in December 1987. The final rule describes the
sampling and analytical protocols to be used in determining whether an abate-
ment activity is complete and the site is clean enough for reoccupancy.
Airborne asbestos concentrations inside the abatement area must be statis-
tically no larger than concentrations outside the abatement area ("outside"
means outside the abatement area, not necessarily outside the building)
before the contractor is released. The rule also describes an initial pre-
screening test that does not compare the concentrations inside the abatement
area with those outside. This prescreening test is permitted to save anal-
ysis costs when airborne asbestos concentrations are so low they cannot be
distinguished from background filter contamination.
AHERA PROTOCOLS
Specific air sampling protocols require the collection of 13 samples--5
samples inside the abatement area, 5 samples outside the abatement area (but
not necessarily outside the building), 2 field blanks, and 1 sealed blank.
Air samples are to be collected after the site has passed a thorough visual
inspection and the area has been aggressively swept to dislodge any remaining
dust. Before air monitoring is begun, floors, walls, and ceilings must be
swept with the exhaust of a leaf blower having a minimum of 1 horsepower.
Stationary fans should be used to provide continuous air circulation—one fan
for each 10,000 cubic feet of workspace. Air samples must be collected on
either 0.4-micrometer (vim) (or smaller) pore-size polycarbonate or 0.45-um
(or smaller) pore-size mixed cellulose ester membrane filters. Each filter
should be mounted on a 5-um pore-size mixed cellulose ester diffusing filter
and cellulose support pad and contained in a three-piece cassette. An
21
-------
TABLE 6. REASONS FOR FAILING NJDOH VISUAL INSPECTIONS AT 15 ASBESTOS-ABATEMENT PROJECTS
Reasons for failing NJOOH visual inspection
Debris in horizontal surfaces
Debris in vertical surfaces
Debris in light fixtures
Debris in wall penetrations
Debris in floors
Debris at floor-wall junctions
Debris at ceiling-wall junctions
Debris in pipes, pipe fittings, pipe hangers
Debris in walls
Debris on skylights
Debris on windows
Debris on structural beams
Debris in electrical wires/fixtures
Debris in storage closets
Debris in shelves
Debris on scaffolding equipment/auxiliary equipment
Debris in ventilation ducts
Debris in clocks
Debris in exit sign
Debris in blackboards
Debris on heating units
Debris in celling gridwork
Debris on door jambs
Debris on counters
Debris behind lockers
Debris behind floor molding
Debris in immovable objects
Abatement iite
A
X
X
X
X
X
B
X
X
X
X
X
X
X
X
X
X
c
X
X
H
X
X
X
X
X
1
X
X
X
X
X
K
X
X
X
X
X
X
X
L
X
M
X
X
X
N
X
X
X
0
X
X
X
P
X
X
X
X
Q
X
X
X
X
X
X
X
R
X
X
X
X
X
s
X
X
X
X
X
X
X
X
X
T
X
X
X
X
X
X
X
Total
6
1
5
6
7
5
5
8
4
2
3
2
3
2
2
3
2
1
1
1
1
1
1
1
1
1
1
ro
ro
-------
extension cowl or retainer ring is also recommended. Air pump flow rates
between 1 and 10 liters per minute should be used for 25-mm cassettes.
TABLE 7. ASBESTOS ANALYSIS OF BULK SAMPLES COLLECTED BY ACS
INSPECTORS DURING THE FINAL VISUAL INSPECTIONS
Site
Total
Number of samples
Collected
Containing asbestos
A
B
C
H
I
K
L
M
N
0
P
Q
R
S
T
6
4
4
0
7
11
1
5
0
0
0
0
33
7
3
6
4
4
0
5
6
1
5
0
0
0
0
32
7
3
81
73
In most cases air-monitoring samples must be analyzed by transmission
electron microscopy (TEM). Laboratories may choose between either the manda-
tory or nonmandatory TEM methods described in the AHERA final rule. The
nonmandatory method supplements the mandatory method by including additional
steps to improve the analysis. Under certain circumstances, a site may be
cleared by phase contrast microscopy (PCM) analysis of samples depending on
the size and nature of the abatement project.
The initial prescreening clearance test permits the five samples col-
lected inside the abatement area to be analyzed and the site cleared if 1) at
least 1199 liters of air are pulled through a 25-mm filter or 2799 liters of
air are pulled through a 37-mm filter, and 2) the arithmetic mean concentra-
tion of these five samples is less than or equal to 70 s/mm2. Otherwise, the
five samples collected outside the abatement area must be analyzed and com-
pared with the samples collected inside the work area by use of a Z-Test.
The Z-Test is carried out by the following calculation:
Z =
Y. - Y
i o
0.8(l/n. + l/nQ)
1/2
23
-------
where Y^ = the average of the natural log of the inside samples
Y = the average of the natural log of the outside samples
n. = the number of samples collected inside the work area
nQ = the number of samples collected outside the work area
If the Z statistic is less than or equal to 1.65, the site passes the
clearance test and the site is considered clean enough for reoccupancy. If
the abatement site does not satisfy either the prescreening test or the
Z-Test, it must be recleaned and a new set of samples collected.
OBSERVED PRACTICES
Aggressive Sampling
Prior to postabatement clearance air monitoring, a 24-hour drying time
is recommended.1 Air monitoring for postabatement clearance should be con-
ducted under aggressive sampling conditions. The abatement area floors,
walls, ledges, ceilings, and other surfaces should be swept with the exhaust
from forced-air equipment (e.g., a minimum 1-horsepower leaf blower) to
dislodge any remaining dust, and stationary fans should be used to keep
fibers suspended during sampling. Current guidance on asbestos-abatement
work practices and procedures recommends aggressive sweeping of the abatement
area for a minimum of 5 minutes per 1000 ft2 of floor area.' The AHERA rule
recommends the use of at least one stationary fan per 10,000 ft3 of workspace
to keep the asbestos fibers suspended during sampling.
Eight of the 20 abatement sites failed to meet the EPA-recommended
drying time of 24 hours after the completion of final cleaning before final
clearance air monitoring was begun. The drying times for these eight sites
ranged from 2 to 18 hours.
Nineteen of the 20 observed abatement sites used aggressive sampling
techniques. Fourteen of these 19 sites failed to meet the recommended ag-
gressive air-sweeping rate of at least 5 minutes per 1000 ft2 of floor area.
Table 8 presents actual and recommended aggressive sampling times for each
observed site. Figure 4 shows the actual aggressive sampling rates per 1000
ft2 of floor area for each of the 20 sites.
Only 12 of the 20 sites used stationary air fans to maintain a constant
air movement during clearance air sampling. Box-type fans were used at nine
of these sites, and pedestal-type fans were used at three sites. Fifteen of
the observed sites failed to use the number of fans per given volume of work-
space required by AHERA. The actual and required number of circulating fans
for each site are presented in Table 8 and shown graphically in Figure 5.
24
-------
TABLE 8. CLEARANCE SAMPLING AND ANALYTICAL PRACTICES OBSERVED
AT 20 ASBESTOS-ABATEMENT SITES
Clearance sampling
Site
A
B
C
D
E
F
G
H
I
J
K
L
M
N
0
P
Q
R
S
T
Flow
rate,
liters/
min
7-19
<10
<10
<10
<10
I10
<10
<10
<10
<10
<10
<10
9.3
9.5
-------
Aggressive Air Sweeping Rate,
Minutes/1000 ft2of Floor Area
PO
CTl
Recommended Agg
Air Sweeping Rate
1000 ft2 of Floor /
D F G
MNOPQRST
SITE
Figure 4. Observed aggressive sweeping times per 1000 square feet
of floor area at 20 asbestos abatement sites.
-------
ro
30
25
20
15
10
5
0
Number of Stationary Fans
n
ABCDEFGHI JKLMNOPQRST
Site
LI Recommended
Actual
Figure 5. Recommended and actual number of stationary fans used during
AHERA clearance air monitoring.
-------
Filter Types
Mixed cellulose ester membrane filters were used in the collection of
clearance air samples at 14 of the 20 observed abatement sites. Polycarbo-
nate membrane filters were used at six sites. The AHERA rule permits the use
of either filter type; however, the pore size must be less than or equal to
0.45 ym for mixed cellulose ester filters and 0.4 ym for polycarbonate
filters. At three sites, 0.8-ym pore-size mixed cellulose ester membrane
filters were used to collect clearance air samples, which did not comply with
the AHERA regulations. All filters used for clearance air monitoring were 25
mm in diameter and were contained in three-piece cassettes with a 50-mm
extension cowl. Table 8 summarizes the type of filter used for clearance air
sampling at each site.
Flow Rates and Air Volumes
Each filter assembly was attached to an electric-powered pump operating
at a specified airflow rate. The air samples were generally collected after
a set length of time so a certain minimum air volume could be achieved. The
AHERA rule states that pump flow rates between 1 and 10 liters per minute may
be used for 25-mm-diameter filters. This was practiced at 18 of the 20 sites
observed. Only at two sites were air samples collected at flow rates greater
than 10 liters per minute. These results are summarized in Table 8. Air
volumes ranged from 1320 to 4161 liters for the postabatement air samples
collected inside and outside the abatement area at the observed sites. The
AHERA rule recommends sampling between 1200 and 1800 liters of air for 25-
mm-diameter filters.
Analytical Methods
At 18 of the 20 observed sites, the laboratory reports indicated that
final clearance air samples were analyzed by TEM in accordance with either
the mandatory or nonmandatory TEM methods described in AHERA (Table 2). At
two sites, phase contrast microscopy was used to analyze the clearance air
samples (Table 2). Although the samples were reportedly analyzed in accord-
ance with NIOSH Method 7400 at these two sites, the clearance samples were
collected using improper filters, i.e., collected using 0.4 ym pore size
polycarbonate filters instead of 0.8 ym pore size mixed cellulose ester
filters specified in the NIOSH Method.
Clearance Tests
Eighteen of the 20 sites were cleared by the AHERA TEM tests. One to
three TEM clearance attempts were made per abatement site. Figure 6 shows
the percentage of sites passing AHERA TEM clearance per attempt. Approxi-
mately 83.3 percent of the sites passed on the first attempt after passing a
thorough visual inspection.
All of the 18 sites ultimately passed the AHERA TEM clearance criterion
of the initial prescreening test (i.e., the average asbestos concentration of
the samples collected inside the abatement area was less than or equal to
70 s/mm2). Three sites initially failed the prescreening test, and two of
28
-------
ro
% Sites Passing AHERA TEM Clearance.
100-
80
60-
40-
20-
83.3%
1st
11.1%
/•
5.6%
~7
2nd
AHERA TEM Clearance Test
3rd
Figure 6. Percentage of 18 sites passing AHERA TEM clearance for
each clearance attempt.
-------
these sites subsequently tried to use the Z-Test to pass clearance. In each
case, the site also failed the Z-Test and had to be recleaned. The Z-Test
was used only twice at the 20 sites observed in this study, and it was never
used to clear the abatement site. Figure 7 presents the average asbestos
concentrations for each clearance attempt for the 18 sites that were cleared
by TEM.
Occasionally, a site passed the initial prescreening test when one or
more of the samples showed an asbestos concentration greater than or equal to
70 s/mm2. As shown in Figure 8, this occurred at three sites in this study.
Three of the 20 sites were inspected by only the AST and subsequently
cleared by TEM. Two of these 3 sites failed the first TEM clearance attempt
after passing the AST visual inspection (see Case Studies E and G). One site
required additional cleaning and passed TEM clearance on the second attempt.
One site required three TEM clearance attempts after additional visual in-
spections by the AST before it was cleared (see Case Study G). Polycarbonate
filters were used to collect air samples at this site. Background asbestos
contamination on the field blanks showed an average asbestos concentration of
53 s/mm2 on the first clearance attempt and 105 s/mm2 on the second attempt.
The field blanks were not analyzed on the third clearance attempt. Of the 15
sites that passed the NJDOH visual inspection, 14 subsequently passed TEM
clearance on the first attempt.
Figure 9 integrates the percentage of sites passing TEM clearance with
the total number of NJDOH visual inspections and TEM clearance attempts. As
shown, the largest percentage (93.5%) of these sites passed the AHERA TEM
clearance on the first attempt after having passed a thorough visual inspec-
tion by the NJDOH. Only 6.7 percent (one site) failed the AHERA TEM clear-
ance after passing a thorough visual inspection. These data support the
premise that effective final cleaning practices that meet the standards of a
thorough visual inspection strongly influence whether the AHERA clearance
test or other TEM clearance tests will be passed.6
One site involved the removal of less than 3000 square feet of asbestos-
containing material. For smaller projects such as this, AHERA permits the
use of phase contrast microscopy to analyze the clearance samples. Five sam-
ples must be collected inside the abatement area and each must have a fiber
concentration of less than or equal to 0.01 f/cm3 of air to pass the clear-
ance criterion. Only one sample was collected at this site, and its fiber
concentration was less than 0.01 f/cm3. Site clearance was based on this one
air sample, which is not in accordance with the five samples required by
AHERA.
One other site was cleared by phase contrast microscopy analysis.
According to AHERA regulations, however, clearance of this site required the
use of the TEM clearance criterion. At this site, only two samples were
collected inside the abatement area, and the fiber concentration associated
with each was less than 0.01 f/cm3. Site clearance was based on these two
samples, where the PCM AHERA clearance criteria require a minimum of five
samples inside the abatement area.
30
-------
300 -
250 -
200 -
150 -
100
50 -
Average Asbestos Concentration, s/mm2
AHERA Prescreening Criterion, 70 a/mm2
111
A B C D E G
H I KLMNOPQRST
Site
1st Attempt
2nd Attempt
3rd Attempt
Figure 7. Average asbestos concentrations for each AHERA clearance
attempt for the 18 sites cleared by TEM.
-------
CO
180 -
160 -
140 -
120 -
100 -
80 -
60 -
40 ~
20 -
0
Asbestos Concentration, s/mm2
AHERA Prescreening Criterion, 70 s/mm
L
SITE
Figure 8. AHERA clearance results for sites with individual sample
concentrations greater than 70 s/mm2.
-------
00
00
30 -
25
20-
15-
10-
5-
0
% Sites Passing AHERA TEM Clearance
6.7%
1
26.7% 26.7% 26.7%
•
0%
1st 2nd 3rd 4th 5th 6th
Total Number of Visual Inspections
0%
7th
6.7%
I
TEM
Clearance
Attempt
Figure 9. Percentage of 15 sites passing AHERA TEM clearance by total
number of ACS visual inspections and AHERA clearance
attempt.
-------
REFERENCES
1. U.S. Environmental Protection Agency. Guidance for Controlling
Asbestos-Containing Materials in Buildings. EPA 560/5-85-024. 1985.
2. American Conference of Governmental Industrial Hygienists. Industrial
Ventilation 18th Edition, A Manual of Recommended Practice. Committee
on Industrial Ventilation. 1984.
3. U.S. Department of Labor, Occupational Safety and Health Administration,
29 CFR Parts 1910 and 1926, Occupational Exposure to Asbestos, Tremo-
lite, Anthophylite, and Actinolite; Final Rules. Federal Register, Vol.
51, No. 119, June 20. 1986.
4. Shagott, D. M. Negative Air Systems. Asbestos Issues. Pages 60-70,
September 1987.
5. U.S. Environmental Protection Agency. Measuring Airborne Asbestos
Following an Abatement Action. EPA 600-4-85-049. November 1985.
6. Kominsky, J. R., J. A. Brownlee, T. J. Powers, R. W. Freyberg. Achieving
a Transmission Electron Clearance Criterion at Asbestos Abatement Sites
in New Jersey. National Asbestos Council Journal, 6(4):25-29, 1989.
34
-------
APPENDIX A
SITE DOCUMENTATION FORM OF FINAL
CLEANING PROCEDURES AND VISUAL INSPECTION
35
-------
I. GENERAL INFORMATION
1. Site number: Form completed by:
2. Building visited:
Address:
3. Removal contractor, address
and phone number
4. ASCM firm, address and
phone number
5. Name of AST:
6. Starting date of abatement:
7. Starting date of final cleaning:
8. Date site cleared:
9. Comments:
36
-------
II. DESCRIPTION OF ABATEMENT SITE
1. Use of site (e.g., classroom, boiler room)
2. Dimensions of all areas within the site and ACM types in those areas.
Area
Dimensions
(W, L, H)
Type of ACM*
(PB, AC, etc.)
Location of ACM
(Pipe, ceiling, etc.)
3. Comments
4. Draw a plan view of the abatement area on the following page.
* ACM types
PB = preformed block (Thermal System Insulation)
AC = air cell (Thermal System Insulation)
LP = layered paper (Thermal System Insulation)
CEM = cementitious insulation (Thermal System Insulation)
BD = asbestos board (Thermal System Insulation)
AP = acoustical plaster (surfacing material)
FP = fireproofing (surfacing material)
CT = ceiling tile (misc. material)
FT = floor tile (misc. material)
TR = transite (misc. material)
PAP = paper-like material (misc. material)
Other (describe)
37
-------
PLAN VIEW OF ABATEMENT AREA
38
-------
III. AIR-FILTRATION UNITS (AFU'S)
1. Location of AFU's (note of plan view of abatement area)
2. Are the AFU's vented to the outside of the building?
Directly Indirectly
Comments:
3. How many AFU's are in use?
4. Types of AFU's
Unit No.
Manufacturer
Model
Unit No.
Manufacturer
Model
5. How frequently are Miters changed?
Prefilter
Intermediate
HEPA
6. Were the filters changed before final cleaning?
Prefilter Intermediate
HEPA
7. Describe source(s) of makeup air:
39
-------
8.
9.
Are visual smoke tests conducted to demonstrate airflow into the abatement
area (i.e., to document negative air-pressure conditions)?
How often?
Where?
Is the negative air pressure monitored by the AST?
If so, how often and where?
10. Measurement of pressure differential (inches W.G.) across critical
containment barriers.
Test Location*
Date
Time
MSMT1
MSMT 2
1
2
3
4
5
* Location of AP measurement shown on plan view of abatement area;
description of each location is presented below.
Comments:
40
-------
NEGATIVE AIR UNIT MEASUREMENT LOG
1 Negative air unit No _
2 Dimensions of negative air intake and locations of velocity measurements
0026D
0082D
0146D
0226D
0342D
0658D
0774D
0854D
0918D
0974D
•w-
Hc
.
.
1
.
.
.
r
.
•
•
•
.
•
.
•
i
\
m
in
Hc=
Measurement locations not more than 6 in apart
Negative air intake face velocity measurements (ft/mm)
Date
Time
MSMT 1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
Average
Test 1
Test 2
Test3
41
-------
IV. FINAL CLEANING PROCEDURES
1. Starting date . Ending date
2. Describe the work practies and procedures used during final cleaning.
42
-------
GENERAL OBSERVATION NOTES ON FINAL CLEANING PROCEDURES
43
-------
V. VISUAL INSPECTION
1. Did the site pass the visual inspection by the AST?
If not, include reasons.
2. Did the site pass the first visual inspection by the ACS inspector?
If not, include reasons.
3. Describe any changes in cleaning methods used prior to the second visual
inspection by the ACS inspector.
4. Did the site pass the second visual inspectin by the ASC inspector?
If not, include reasons.
44
-------
5. Describe any changes in cleaning methods used prior to the third visual
inspection by the ACS inspector.
6. Did the site pass the third visual inspection by the ACS inspector?
If not, include reasons.
7. Describe any changes in cleaning methods used prior to the fourth visual
inspection by the ACS inspector.
8. Did the site pass the fourth visual inspection by the ACS inspector?
If not, include reasons.
9. Describe any changes in cleaning method used prior to the fifth visual
inspection by the ACS inspector.
45
-------
APPENDIX B
SITE DOCUMENTATION FORM OF
AHERA CLEARANCE PRACTICES
46
-------
1. Did the AST conduct aggressive air sweeping of surfaces?
If yes, for how long? minutes.
2. Were fans used to maintain aggressive air turbulence conditions during
clearance sampling? .
Type:
Size (dia. blades) How many?
Pedestal
Box
Other
3. Air sampling filter media and cassette.
w/50-mm cowl w/o 50-mm cowl
25-mm, 0.8 u MCE
25-mm, 0.45 n MCE
25-mm, 0.4 n PC
Other
4. Air sampling flow rate (range) L/min.
5. Comments:
47
-------
6. Measurement of pressure differential (inches W.G.) across critical
containment barriers.
Test Location*
Date
Time
MSMT1
l
2
3
4
5
6
7
8
9
10
* Location of AP measurement shown on plan view of abatement area;
description of each location is presented below.
Comments:
48
-------
NEGATIVE AIR UNIT MEASUREMENT LOG
1 Negative air unit No
2 Dimensions of negative air intake and locations of velocity measurements
0026D
0082D
0146D
0226D
0342D
0658D
0774D
0854D
0918D
0974D
D =
m
LJ
Hc
w=
w.
C
•
•
I
k
n
m
v
•
•
r
d
v
•
•
H
H
•
•
•
c=
1
1
1
in
in
Measurement locations not more than 6 in apart
Negative air intake face velocity measurements (ft/mm)
Date
Time
MSMT 1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
Average
Testl
Test 2
Test3
49
-------
APPENDIX C
CASE STUDIES
50
-------
CASE HISTORY A
SITE DESCRIPTION
This abatement project involved removal of approximately 19,100 ft2 of
spray-applied asbestos-containing ceiling plaster from a single-story school
building. The abatement area included corridors, classrooms, offices, and
recreational rooms. The project specification indicated that the asbestos
content of the ceiling plaster was approximately 5 to 10 percent chrysotile.
VENTILATION AND NEGATIVE AIR PRESSURE
Six high-efficiency particulate air (HEPA) filtration units were oper-
ated during the final cleaning period, and 11 were operated during AHERA
clearance sampling. Table A-l presents the measured air-intake volume for
each unit. The average air-intake volume was approximately 1666 ft3/min
during final cleaning and 1648 ft3/min during AHERA clearance sampling.
Based on the volume of the work area (280,000 ft3) and the combined average
air-intake volumes, the air exchange rates were approximately 2.1 air changes
per hour during final cleaning and 3.9 air changes per hour during AHERA
clearance sampling.
Figures A-l and A-2 compare the measured air-intake volume of each
HEPA-filtration unit operating during final cleaning and AHERA clearance
sampling, respectively, with the unit's nominal airflow. The actual operat-
ing percentage of the nominal airflow ranged from 82 to 84 during final
cleaning and 81 to 84 during AHERA clearance sampling.
Table A-2 presents the static pressure differential measured across the
containment barriers at three locations. The number of locations tested was
determined by available access to the critical containment barriers. The
static pressure differential ranged from 0.00 to -0.01 in. water during final
cleaning and -0.02 to -0.03 in. water during AHERA clearance sampling. The
increased differential pressure is most likely attributable to the additional
number of HEPA-filtration units that were operating.
The asbestos safety technician (AST) continually monitored the static
pressure differential at Test Location 2 during final cleaning. These mea-
surements showed a static pressure differential of -0.01 to -0.02 in. water.
The project specification required maintenance of a minimum static pressure
differential of -0.02 in. water across the containment barrier.
51
-------
TABLE A-l. AIRFLOW PERFORMANCE OF HEPA-FILTRATION UNITS
Airflow, ft3
Model
1
1
1
1
1
1
1
1
1
1
1
1
1
2
2
2
2
Unit
1
2
3
4
5
6
1
2
3
4
5
6
7
8
9
10
11
Mean Min.
1649
1685
1680
1649
1696
1638
AHERA
1680
1670
1628
1649
1659
1612
1680
1643
1649
1617
1638
Final
1344
1512
1344
1344
1512
1344
/min.
Max.
cleaning
1764
1848
1848
1848
1848
1848
clearance sampl
1596
1428
1344
1344
1512
1344
1344
1344
1344
1344
1344
1848
1848
1848
1848
1848
1932
1848
1848
1848
1848
1848
Std.
dev.
118
91
122
118
95
122
ing
73
107
139
145
81
163
126
129
122
141
126
95% Confidence
interval
Lower
1585
1637
1615
1585
1645
1573
1641
1613
1554
1571
1613
1525
1613
1574
1584
1542
1571
Upper
1712
1734
1745
1712
1746
1677
1719
1726
1701
1726
1702
1699
1747
1712
1713
1692
1705
TABLE A-2. STATIC PRESSURE DIFFERENTIALS
ACROSS CONTAINMENT BARRIERS
(in. water)
Test location
Final cleaning AHERA clearance
1
2
3
-0.01
-0.01
-0.01
-0.02
-0.03
-0.02
52
-------
en
u>
Percent of Nominal Airflow
100
80
60
40
20
82%
84%
84%
82%
•
•
85%
5
82%
6
HEPA Filtration Unit
(Same Model)
Figure A-1. Airflow performance for HEPA filtration systems
operating during final cleanup.
-------
Percent of Nominal Airflow
100-
80-
8 9 10 11
HEPA Filtration Unit
Model 1
Model 2
Figure A-2. Airflow performance for HEPA filtration systems
operating during AHERA clearance.
-------
In addition to continually monitoring the differential pressure, the AST
used ventilation smoke tubes for visually checking negative pressure (i.e.,
direction of airflow through openings in the containment barrier, such as the
decontamination facility and waste load-out port). Reportedly, these quali-
tative checks were performed each morning.
The HEPA-filtration units were placed so that the makeup air entered the
work area through the personnel decontamination facility and waste load-out
port. Ten of the 11 operating units were positioned along exterior walls
to facilitate venting the exhaust through windows via an interconnected
flexible duct. The exhaust of 1 of the 11 units was vented through a doorway
via an interconnected flexible duct that passed through a classroom outside
of the abatement area. This is particularly noteworthy because the flexible
duct was torn and a percentage of the exhaust air was released into the
building. The discharge air from the HEPA-filtration units was not monitored
for fiber content.
The contractor, who was responsible for maintaining the HEPA-filtration
units, stated that the prefliters, secondary filters, and HEPA filters were
changed before final cleaning was initiated. Thereafter, the prefiHers and
secondary filters were changed when they became "visibly dirty." The HEPA
filters were changed every 600 to 700 hours (as recommended by the manu-
facturer) or when an audible alarm was actuated by a differential pressure
sensor set by the manufacturer.
FINAL CLEANING
Personal Protective Equipment
The personal protective equipment worn by the workers during final
cleaning consisted of full-body disposable coveralls and either full- or
half-facepiece air-purifying respirators equipped with dual-cartridge HEPA
filters.
Cleaning Procedures
Final cleaning began after the encapsulated plastic sheeting was removed
from the walls, floors, light fixtures, and other surfaces. The critical
barriers, windows, doors, and heating, ventilation, and air-conditioning
(HVAC) vents remained sealed. The HEPA-filtration units remained in service.
Final cleaning was organized so the workers began in the areas farthest
from the personnel decontamination facility and worked toward it. No as-
sociation appeared to exist between the work direction and the location of
the HEPA-filtration units.
Final cleaning began with the spraying of plaster and masonry walls,
windows, plastic critical containment barriers, and other vertical surfaces
with a light water mist to remove any visible debris. The resultant asbes-
tos-containing water on the floor was gathered into pools by use of a rubber
55
-------
squeegee. The bulk of the pooled water was scooped up with plastic-bladed
shovels, an approach that worked surprisingly well. The water was put into
double-layered, 6-mil-thick asbestos-disposal bags, which generally contained
plastic that had been removed from the walls and floors. The residual water
removed with a wet vacuum was also placed in these bags.
Some of the asbestos-containing water penetrated the seams between the
vinyl floor tiles and caused sections to buckle. The buckled sections were
sporadically distributed throughout the abatement area. The asbestos-con-
taining water beneath the floor tiles was allowed to dry, and the tiles were
not repaired. These areas could be potential sources of airborne asbestos
fibers when repaired later by maintenance personnel.
After the surfaces had dried, a vacuum equipped with a HEPA filter was
used to clean crevices around windows, doors, and shelves; floor-wall inter-
faces; etc.
All of the vertical and horizontal surfaces were then wet-cleaned with
amended water. The contractor reportedly prepared the amended water solution
by mixing approximately 2 ounces each of 50 percent polyoxyethylene ester and
50 percent polyoxyethylene ether in 5 gallons of water.
The elevated horizontal and vertical surfaces were wiped first and then
all other surfaces. All the surfaces except the floors were wiped with
cotton rags dampened with amended water. A bucket of amended water was
either used by a single worker or shared by several workers. The workers did
not appear to wipe the surfaces in any one direction. The cloth rags were
not replaced frequently, particularly during the cleaning of elevated and
hard-to-access surfaces. Nor was the amended water changed frequently.
After the walls, windows, and other surfaces (shelves, ledges, counters,
plastic-covered HEPA-filtration systems and associated exhaust ducts, etc.)
were wet-wiped, the floor was mopped with a clean mop head that was wetted
with amended water. No change in the water was observed during this proce-
dure.
The last step in final cleaning effort involved removal of the plastic
sheeting covering the HEPA-filtration units and associated exhaust ducts.
The latter were covered with a plastic sleeve. According to the contractor,
this simplified cleaning of this equipment.
Final cleaning involved one complete wet-cleaning of all surfaces. No
aggressive cleaning (i.e., air sweeping of all vertical and horizontal sur-
faces to dislodge any remaining particulate) was conducted.
Wastewater from the wet-wiping and mopping operations was treated as
asbestos-containing water and placed in double-layered 6-mil-thick standard
disposal bags. These standard asbestos disposal bags which contained
wastewater were not placed in leak-tight containers or solidified with a
gelling compound. The rags and mop heads used during cleaning also were
placed in these bags. The bags were not wet-wiped with amended water before
being removed from the abatement area.
56
-------
Upon completing final cleaning, the abatement contractor requested a
final visual inspection by an onsite AST, who was the building owner's repre-
sentative. The AST conducted the visual inspection within 2 hours after
notification. The AST identified several areas, particularly elevated hori-
zontal surfaces, that required further cleaning. After these designated
areas were recleaned, the AST conducted a final walk-through inspection to
assure that the identified areas were clean.
FINAL VISUAL INSPECTION BY NEW JERSEY DEPARTMENT OF HEALTH, ASBESTOS CONTROL
SERVICE
The site failed the first two visual inspections because of the presence
of live electrical outlets inside the containment and the presence of asbes-
tos-contaminated water in the toilets of the men's restroom and in the sink
in the janitor's closet. Workers were observed dumping the contaminated mop
water into drains, toilets, and sinks.
The site failed the third visual inspection because of the presence of
debris on several skylights, on horizontal surfaces, in wall penetrations,
and at the top of wooden and concrete walls. Pipe wrap was also left on
pipes. Six bulk samples were collected to characterize the residual debris
found on skylights, above windows, and in wall penetrations and the pipe wrap
that was left. Chrysotile asbestos was identified in all samples. The
asbestos content of the debris found in wall penetrations was approximately 6
percent chrysotile. The asbestos content of the pipe wrap was approximately
17 percent. All other samples were not sufficiently large to quantify the
asbestos content.
The site passed the fourth visual inspection.
AHERA CLEARANCE SAMPLING BY AST
The AHERA clearance sampling was initiated approximately 18 hours after
the site passed the visual inspection. Using a hand-held electric leaf
blower, the AST conducted aggressive blowdown of vertical and horizontal
surfaces for approximately 25 minutes, which is equivalent to approximately 5
minutes per 3800 square feet of floor area. No floor fans were used subse-
quently to maintain air turbulence during sampling.
The clearance air samples were collected on 25-mm, 0.8-um pore size,
mixed cellulose ester membrane filters contained in a three-piece cassette
with a 50-mm conductive cowl. The samples were collected at flow rates
ranging from 7 to 19 liters per minute. The laboratory report indicates that
the samples were analyzed in accordance with the AHERA mandatory TEM method.
Table A-3 presents the results of clearance samples the AST collected
inside the abatement area. The samples met the initial AHERA clearance
criterion, i.e., an average asbestos concentration of less than 70 structures
per square millimeter (s/mm2). The average asbestos concentration for the
five inside samples was 0 s/mm2.
57
-------
TABLE A-3. AHERA CLEARANCE SAMPLE RESULTS
Sample
Location
Inside
Inside
Inside
Inside
Inside
Sample volume,
liters
4161
4000
3008
2226
4088
Asbestos
s/mm2
0
0
0
0
0
concentration,
s/cm3
<0.0041b
<0.0042b
<0.0045b
<0.0042b
<0.0041b
Outdoor samples and blanks were not analyzed because the aver-
age asbestos concentration for the five inside samples was less
than 70 s/mm2.
Sensitivity of the analytical method.
58
-------
CASE HISTORY B
SITE DESCRIPTION
This abatement project involved removal of approximately 5400 ft2 of
spray-applied asbestos-containing acoustical plaster from ceilings and
fascias on the second floor of a two-story school building. The abatement
area included corridors, classrooms, and offices. The project specification
indicated that the asbestos content of the ceiling plaster was approximately
2 to 6 percent chrysotile.
VENTILATION AND NEGATIVE AIR PRESSURE
Performance of the two high-efficiency particulate air (HEPA) filtration
units that operated during the final cleaning period was not measured. Two
HEPA filtration units also were operated during AHERA clearance sampling;
Table B-l presents the measured air-intake volume of each of these units.
The average air-intake volume was 1709 ft3/min during AHERA clearance sam-
pling. Based on the volume of the work area (50,000 ft3) and the combined
average air-intake volume, the air exchange rate was approximately 4.1 air
changes per hour during AHERA clearance sampling.
TABLE B-l. AIRFLOW PERFORMANCE OF HEPA-FILTRATION UNITS
DURING AHERA CLEARANCE SAMPLING
3 95% Confidence
Airflow, ft /min. interval
Model Unit Mean Min. Max. dev. Lower Upper
1 1 1712 1512 1848 107 1655 1769
1 2 1706 1512 1848 102 1652 1760
Figure B-l compares the measured air-intake volume of each HEPA-filtra-
tion unit operating during AHERA clearance sampling with the unit's nominal
airflow. The actual operating percentages of the nominal air flow were 85
and 86 during AHERA clearance sampling.
Table B-2 presents the static pressure differential measured across the
containment barriers at two test locations. The number of locations tested
59
-------
Percent of Nominal Airflow
a-.
o
100
80
60
40
20
86%
85%
HEPA Filtration Unit
(Same Model)
Figure B-1. Airflow performance for HEPA filtration systems
operating during AHERA clearance.
-------
was determined by available access to the critical containment barriers. As
shown, static pressure differential was -0.02 in. water during final cleaning
and -0.02 in. water during AHERA clearance sampling.
TABLE B-2. STATIC PRESSURE DIFFERENTIALS
ACROSS CONTAINMENT BARRIERS
(in. water)
Test location Final cleaning AHERA clearance
1
2
-0.02
-0.02
-0.02
-0.02
The asbestos safety technician (AST) did not monitor the static pressure
differential across the containment barriers. Instead, ventilation smoke
tubes were used to check negative pressure visually (i.e., the direction of
airflow through openings in the containment barrier, such as the decontami-
nation facility and waste load-out port). Reportedly, these qualitative
checks were performed each morning before the workshift and twice during the
workshift.
The HEPA-filtration units were placed so that the makeup air entered the
work area through the personnel decontamination facility and waste load-out
port. The two operating units were positioned along exterior walls to facil-
itate venting of the exhaust through windows via an interconnected flexible
duct. The discharge air from the HEPA-filtration units was not monitored for
fiber content.
The contractor who was responsible for maintaining the HEPA-filtration
units, stated that the prefilters, secondary filters, and HEPA filters were
changed before final cleaning was initiated. Thereafter, the prefilters and
secondary filters were changed when they became "visibly dirty." The HEPA
filters were changed every 600 to 700 hours (as recommended by the manu-
facturer) or when an audible alarm was actuated by a differential pressure
sensor set by the manufacturer.
FINAL CLEANING
Personal Protective Equipment
The personal protective equipment worn by the workers during final
cleaning consisted of full-body disposable coveralls and either full- or
half-facepiece air-purifying respirators equipped with dual-cartridge HEPA
filters.
Cleaning Procedures
Final cleaning began after the removal of the encapsulated plastic
sheeting from the walls, floors, and other surfaces. The critical barriers,
61
-------
windows, doors, fixed objects, and heating, ventilation, and air-conditioning
(HVAC) vents remained sealed. The HEPA filtration units remained in service.
Final cleaning was organized so the workers began in the areas farthest
from the personnel decontamination facility and worked toward it. No as-
sociation appeared to exist between the work direction and the location of
HEPA-filtration units.
Final cleaning began with scraping and brushing of the ceiling-wall
intersection areas to remove any residual debris on the substrate. Any
resultant debris that fell to the floor was then removed with a HEPA-filtered
vacuum. Hard-to-reach places (such as crevices around windows and doors) and
floor-wall intersections were also cleaned with a HEPA-filtered vacuum.
Vertical and horizontal surfaces were then wet-cleaned with amended
water. The amended water solution, which was prepared by the contractor,
reportedly consisted of a mixture of approximately 1 ounce each of 50 percent
polyoxyethylene ester and 50 percent polyoxyethylene ether in 5 gallons of
water.
The elevated horizontal and vertical surfaces were wiped first, and then
all other surfaces were wiped. All surfaces except the floors were wiped
with cotton rags dampened with amended water. The workers did not appear to
wipe the surfaces in any one direction. A bucket of amended water was either
used by a single worker or shared by several workers. The same bucket was
used for rinsing and dampening the rags. The cloth rags were not replaced
frequently, particularly during the cleaning of elevated and hard-to-access
surfaces. Nor was the amended water changed frequently.
After the walls, windows, and other surfaces (shelves, ledges, plastic-
covered fixed objects, etc.) were wet-wiped, the floor was dry-swept and
immediately thereafter mopped with a clean mop head wetted with amended
water. No change in the water was observed during this procedure.
The last cleaning effort involved wet-cleaning easily accessible hori-
zontal surfaces, and a complete wet-mopping of the floors with amended water.
No aggressive cleaning (i.e., air sweeping of all vertical and horizon-
tal surfaces to dislodge any remaining particulate) was conducted.
Wastewater from the wet-wiping and mopping operations was treated as
asbestos-containing water and placed in double-layered 6-mil-thick standard
disposal bags. These standard asbestos disposal bags which contained waste-
water were not placed in leak-tight containers or solidified with a gelling
compound. The rags and mop heads used during cleaning were also placed in
these bags. The bags were not wet-wiped with amended water before being
removed from the abatement area.
Upon completing final cleaning, the abatement contractor requested a
final visual inspection by an onsite AST who was the building owner's
representative. The AST conducted the visual inspection within 2 hours after
62
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notification. The AST identified several areas, particularly elevated hori-
zontal surfaces and ceiling-wall intersections, that required further clean-
ing. After these designated areas were recleaned, the AST conducted a final
walk-through inspection to assure that the identified areas were clean.
FINAL VISUAL INSPECTION BY NEW JERSEY DEPARTMENT OF HEALTH, ASBESTOS CONTROL
SERVICE
The site failed the first visual inspection because of the presence of
gross debris (both granular and fluffy) 1) on tops of closets, 2) in the
corners of window sills, 3) at floor-wall and ceiling-wall junctions, 4) in
cracks and crevices, 5) on ceiling rafters and beams, 6) on floors, and 7) on
auxiliary equipment. Four bulk samples were collected to characterize the
makeup of the residual debris. Samples were collected from the top of a
closet, from window jambs, and from a wall-ceiling junction. Asbestos was
identified in each sample collected; however, the samples were not suf-
ficiently large to quantify the percentage of asbestos in each.
The site failed the second visual inspection because of debris on
clocks, windows, ceiling beams, tops of blackboards, and horizontal surfaces
in the classrooms and closets. The site passed the third visual inspection.
AHERA CLEARANCE SAMPLING BY AST
The AHERA clearance sampling was initiated approximately 24 hours after
the site passed the visual inspection. Using a hand-held electric leaf
blower, the AST conducted aggressive air sweeping of vertical and horizontal
surfaces for approximately 20 minutes, which is equivalent to approximately 5
minutes per 1350 square feet of floor area. Five 18-inch-diameter box-type
floor fans were subsequently used to maintain air turbulence during clearance
sampling.
The clearance air samples were collected on 25-mm, 0.8-ym pore size,
mixed cellulose ester membrane filters contained in a three-piece cassette
with a 50-mm conductive cowl. The samples were collected at flow rates
ranging from 9.5 to 10 liters per minute. The laboratory report indicates
the samples were analyzed in accordance with the AHERA mandatory TEM method.
Table B-3 presents the results of clearance samples the AST collected
inside the abatement area. The samples met the initial AHERA clearance
criterion, i.e., an average asbestos concentration below 70 structures square
millimeter (s/mm2). The average asbestos concentration for the five inside
samples was 0 s/mm2.
63
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TABLE B-3. AHERA CLEARANCE SAMPLE RESULTS
Asbestos concentration
Sample
location
Inside
Inside
Inside
Inside
Inside
Sample volume,
liters
1500
1500
1500
1500
1500
s/mm2
0
0
0
0
0
s/cm3
<0.005b
<0.005b
<0.005b
<0.005b
<0.005b
a Outside samples and blanks were not analyzed because the average
asbestos concentration for the five inside samples was less
than 70 s/mm2.
Sensitivity of the analytical method.
64
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CASE HISTORY C
SITE DESCRIPTION
This abatement project involved removal of thermal system insulation
from a three-story school building. The asbestos-containing materials
included insulation on the boiler, water tank, and fan duct in the boiler
room and preformed block and air-cell-paper pipe insulation in the boiler
room and adjacent corridors.
The project specification indicated that the asbestos content of the
preformed block, air-cell-paper, and cementitious surface insulation was
approximately 40 to 60 percent chrysotile. The specifications did not quan-
tify the amount of asbestos-containing material in each location.
VENTILATION AND NEGATIVE AIR PRESSURE
Four high-efficiency particulate air (HEPA) filtration units were
operated during the final cleaning period and during AHERA clearance sam-
pling. Table C-l presents the measured air-intake volume for each unit.
The average air-intake volume was 1414 ft3/min during final cleaning and
1412 ft3/min during AHERA clearance sampling. Based on the volume of the
work area (32,000 ft3) and the combined average air-intake volumes, the air
exchange rates were approximately 10.7 air changes per hour during final
cleaning and 10.6 air changes per hour during AHERA clearance sampling.
Figures C-l and C-2 compare the measured air-intake volume for each
HEPA-filtration unit operating during final cleaning and AHERA clearance
sampling, respectively, with the unit's nominal airflow. The actual oper-
ating percentages of the nominal airflow ranged from 72 to 86 during final
cleaning and 72 to 84 during AHERA clearance sampling.
Table C-2 presents the static pressure differential measured across the
containment barriers. The number of locations tested was determined by
available access to the critical containment barriers. The static pressure
differential was -0.01 in. water during final cleaning and ranged from -0.01
to -0.02 in. water during AHERA clearance sampling.
The asbestos safety technician (AST) did not monitor the static pressure
differential across the containment barriers. Instead, smoke tubes were
used to check negative pressure visually (i.e., direction of airflow through
openings in the containment barrier, such as the decontamination facility and
waste load-out port). Reportedly, these qualitative checks were performed
each morning before the workshift.
65
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TABLE C-l. AIRFLOW PERFORMANCE OF HEPA-FILTRATION UNITS
Model
Airflow, ft /min
Unit Mean Min.
Max.
Std.
dev.
95% Confidence
interval
Lower Upper
Final cleaning
1
2
2
2
1
2
3
4
721
1712
1591
1633
652
1428
1176
1344
815
1932
1848
1848
57
168
191
145
690
1622
1489
1555
751
1801
1693
1710
AHERA clearance sampling
1
2
2
2
1
2
3
4
718
1680
1575
1675
652
1512
1260
1512
815
1932
1848
1764
45
129
147
69
694
1611
1497
1638
742
1749
1653
1712
TABLE C-2. STATIC PRESSURE DIFFERENTIALS
ACROSS CONTAINMENT BARRIERS
(in. water)
Test location
Final cleaning AHERA clearance
1
2
-0.01
-0.01
-0.01
-0.02
66
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Percent of Nominal Airflow
100 -
80
2 3
HEPA Filtration Unit
Model 1
Model 2
Figure C-1. Airflow performance for HEPA filtration systems
operating during final cleanup.
-------
Percent of Nominal Airflow
00
100 -f
80
60 ^
40 -
20
72%
84%
79%
84%
2 3
HEPA Filtration Unit
Model 1
Model 2
Figure C-2. Airflow performance for HEPA filtration systems
operating during AHERA clearance.
-------
The HEPA-filtration units were placed so that the makeup air entered the
work area through the personnel decontamination facility and waste load-out
port. Two of the four operating units were positioned along exterior walls
to facilitate venting of the exhaust through windows via an interconnected
flexible duct. The exhaust of two of the four units was vented through a
doorway via an interconnected flexible duct that passed through a classroom
outside of the abatement area. This is particularly noteworthy because as
the flexible duct for one of the units was torn and a percentage of the
exhaust air was released into the building. The discharge air from the
HEPA-filtration units was not monitored for fiber content.
The contractor, who was responsible for maintaining the HEPA-filtration
units, stated that the prefilters, secondary filters, and HEPA filters were
changed before final cleaning was initiated. Thereafter, the prefilters and
secondary filters were changed when they became "visibly dirty." The HEPA
filters were changed every 600 to 700 hours (as recommended by the manu-
facturer) or when an audible alarm was actuated by a differential pressure
sensor set by the manufacturer.
FINAL CLEANING
Personal Protective Equipment
The personal protective equipment worn by the workers during final
cleaning consisted of full-body disposable coveralls and either full- or
half-facepiece air-purifying respirators equipped with dual cartridge HEPA
filters.
Cleaning Procedures
Final cleaning began after the removal of the encapsulated plastic
sheeting from the walls, floors, and other surfaces. The windows, doors,
fixed objects, and heating, ventilation, and air-conditioning (HVAC) vents
remained sealed. The HEPA-filtration units remained in service.
Final cleaning was organized so the workers began in the areas nearest
to the personnel decontamination facility and worked away from it. No
association appeared to exist between the work direction and the location of
HEPA-filtration units.
Final cleaning began with the wire-brushing of abated surfaces (pipes,
boilers, tanks, and ventilation ducts) to remove any residual debris from the
substrate. A fine-bristle brush, (e.g., a draftsman's brush) was then used
to sweep the surfaces, after which they were wet-cleaned with absorbent paper
towels dampened in amended water containing a standard surfactant mixture
plus a penetrating encapsulant. A bucket containing the amended water with
the encapsulant was most often used by a single worker. The paper towels
were replaced frequently; however, occasionally they were not replaced until
they began to deteriorate as a result of wiping rough surface's. The amended
water was not changed frequently.
69
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After the surfaces had dried, a vacuum equipped with a HEPA filter was
used to clean crevices around windows, doors, and shelves; floor-wall inter-
faces; etc. All other vertical and horizontal surfaces were then wet-cleaned
with the amended water mixture described earlier.
The elevated horizontal and vertical surfaces were wiped first, and then
all other surfaces were wiped. All of the surfaces except the floors were
wiped with absorbent paper towels that had been dampened with the amended
water. A bucket of amended water was either used by a single worker or
shared by several workers. Although the workers did not appear to wipe the
surfaces in any one direction, they approached this effort rather meticulous-
ly. Although the paper towels were reused, such reuse appeared to be
markedly less than that observed for cotton rags at other sites. The absor-
bent paper towels seemed to work well on smooth surfaces. The amended water
was not changed frequently.
After the-walls and other surfaces (plastic-covered fixed objects) had
been wet wiped, the floor was mopped with a clean mop head wetted with the
amended water mixture. No change in the water was observed during this
procedure.
The final cleaning effort involved a complete wet-mopping of the floors
with a clean mop head and clean amended water. No aggressive cleaning (i.e.,
air sweeping of all vertical and horizontal surfaces to dislodge any remain-
ing particulate) was conducted.
Wastewater from the wet-wiping and mopping operations was treated as
asbestos-containing water and placed in double-layered 6-mil-thick standard
disposal bags. These standard asbestos disposal bags which contained
wastewater were not placed in leak-tight containers or solidified with a
gelling compound. The paper towels and mop heads used during cleaning also
were placed in these bags. The bags were not wet-wiped with amended water
before being removed from the abatement area.
Upon completing final cleaning, the abatement contractor requested a
final visual inspection by an onsite AST, who was the building owner's repre-
sentative. The AST conducted the visual inspection within 2 hours after
notification. The AST identified several areas, particularly around pipe and
ventilation duct hangars, that required further cleaning. After these
designated areas were recleaned, the AST conducted a final walk-through
inspection to assure that the identified areas were clean.
FINAL VISUAL INSPECTION BY NEW JERSEY DEPARTMENT OF HEALTH, ASBESTOS CONTROL
SERVICE
Some minor debris was found on pipe elbows and joints and on some hori-
zontal surfaces. These elbows, joints, and horizontal surfaces were cleaned
while the inspector was in the containment area, and the site subsequently
passed the first visual inspection. Four bulk samples were collected from
pipe elbows to characterize the residual debris. Asbestos was identified in
each sample; however, the samples were not large enough to quantify the
percentage of asbestos in each.
70
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AHERA CLEARANCE SAMPLING BY AST
The AHERA clearance sampling was initiated approximately 24 hours after
the site passed the visual inspection. Using a hand-held electric leaf
blower, the AST conducted aggressive air sweeping of vertical and horizontal
surfaces for approximately 30 minutes, which is equivalent to approximately 5
minutes per 270 square feet of floor area. No floor fans were used subse-
quently to maintain air turbulence during sampling.
The clearance air samples were collected on 25-mm, 0.45-pm pore size,
mixed cellulose ester membrane filters contained in a three-piece cassette
with a 50-mm conductive cowl. The samples were collected at a flow rate of
9.25 liters per minute. The laboratory report, indicates that the samples
were analyzed in accordance with the AHERA mandatory TEM method.
Table C-3 presents the results of clearance samples the AST collected
inside the abatement area. The samples met the initial AHERA clearance
criterion, i.e., an average asbestos concentration below 70 structures per
square millimeter (s/mm2). The average asbestos concentration for the five
inside samples was 44 s/mm2.
Sample
location
Inside
Inside
Inside
Inside
Inside
TABLE C-3. AHERA
Sample volume
liters
2091
2091
2091
2100
2100
CLEARANCE SAMPLE RESULTS
Asbestos concentration
>
s/mm2 s/cm3
0 <0.005b
0 <0.005b
0 <0.005b
29 0.005
58 0.010
Outside samples and blanks were not analyzed because the aver-
age asbestos concentration for the five inside samples was less
than 70 s/mm2.
Sensitivity of the analytical method.
71
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CASE HISTORY D
SITE DESCRIPTION
This abatement project involved removal of spray-applied asbestos-con-
taining ceiling plaster and thermal system insulation from a single-story
school building. The ceiling plaster and its expanded metal lathe substrate
were removed from a boiler room, a mechanical storage room, and an electrical
distribution room. The thermal system insulation was removed from mechanical
equipment (i.e., water tank, pipe joints, elbows, and fittings) in a boiler
room.
The project specification indicated that the asbestos content of the
ceiling plaster was approximately 20 to 35 percent chrysotile, and that the
thermal insulation on the mechanical equipment surfaces was 40 to 60 percent
chrysotile. The project specifications did not quantify the amount of asbes-
tos-containing material in each location.
VENTILATION AND NEGATIVE AIR PRESSURE
Three high-efficiency particulate air (HEPA) filtration units were
operated during the final cleaning period, and three were operated during
AHERA clearance sampling. Table D-l presents the measured air-intake volume
for each unit. The average air-intake volume was 1778 ft3/min during final
cleaning and 1762 ft3/min during AHERA clearance sampling. Based on the
volume of the work area (44,200 ft3) and the combined average air-intake
volumes, the air-exchange rates were approximately 7.2 air changes per hour
during final cleaning and 7.1 air changes per hour during AHERA clearance
sampling.
Figures D-l and D-2 compare the measured air-intake volume of each
HEPA-filtration unit operating during final cleaning and AHERA clearance
sampling, respectively, with the unit's nominal airflow. The actual oper-
ating percentages of the nominal airflow ranged from 84 to 97 during final
cleaning and 79 to 99 during AHERA clearance sampling. The reason for the
significantly higher operating airflow performance of the third air filtra-
tion unit is not known.
Table D-2 presents the static pressure differential measured across the
containment barriers at two locations. The number of locations tested was
determined by available access to the critical containment barriers. The
static pressure differential was -0.01 to -0.02 in. water during final clean-
ing and -0.02 in. water during AHERA clearance sampling.
72
-------
Percent of Nominal Airflow
100 -1
80
60 -
40 -
20 -
85%
84%
HEPA Filtration Unit
Model 1
Model 2
Figure D-1. Airflow performance for HEPA filtration systems
operating during final cleanup.
-------
Percent of Nominal Airflow
100 -i
80-
60 -
40
20 -
0 -
87%
79%
HEPA Filtration Unit
Model 1
Model 2
Figure D-2. Airflow performance for HEPA filtration systems
operating during AHERA clearance.
-------
TABLE D-l. AIRFLOW PERFORMANCE OF HEPA-FILTRATION UNITS
3
Airflow, ft /min
Model
1
1
2
Unit
1
2
3
Mean
1709
1680
1946
Min.
Final
1428
1344
1719
Max.
cleaning
1882
1848
2101
Std.
dev.
141
133
89
95% Confidence
interval
Lower
1634
1609
1899
Upper
1784
1751
1993
AHERA clearance sampling
1
1
2
1
2
3
1735
1580
1970
1344
1176
1815
1865
1848
2101
141
171
95
1660
1489
1919
1B10
1671
2020
TABLE D-2. STATIC PRESSURE DIFFERENTIALS
ACROSS CONTAINMENT BARRIERS
(in. water)
Test location
Final cleaning
AHERA clearance
1
2
-0.02
-0.01
-0.02
-0.02
75
-------
The asbestos safety technician (AST) did not monitor the static pressure
differential across the containment barriers. Instead, ventilation smoke
tubes were used to check negative pressure visually (i.e., direction of
airflow through openings in the containment barrier, such as the decontamina-
tion facility and waste load-out port). Reportedly, these qualitative checks
were performed each morning before the workshift and twice during the work-
shift.
The HEPA-filtration units were placed so that the makeup air entered the
work area through the personnel decontamination facility and waste load-out
port. The four operating units were positioned along exterior walls to
facilitate venting of the exhaust through windows via an interconnected
flexible duct. The discharge air from the HEPA-filtration units was not
monitored for fiber content.
The contractor, who was responsible for maintaining the HEPA-filtration
units, stated that the prefilters, secondary filters, and HEPA filters were
changed before final cleaning was initiated. Thereafter, the prefilters and
secondary filters were changed when they became "visibly dirty." The HEPA
filters were changed every 600 to 700 hours (as recommended by the manu-
facturer) or when an audible alarm was actuated by a differential pressure
sensor set by the manufacturer.
FINAL CLEANING
Personal Protective Equipment
The personal protective equipment worn by the workers during final
cleaning consisted of full-body disposable coveralls, and either full- or
half-facepiece air-purifying respirators equipped with dual-cartridge HEPA
filters.
Cleaning Procedures
Final cleaning began after the removal of the encapsulated plastic
sheeting from the walls, floors, and other surfaces. The critical barriers,
windows, doors, fixed objects, and heating, ventilation, and air-conditioning
(HVAC) vents remained sealed. The HEPA filtration units remained in service.
Final cleaning was organized so the workers began in the areas nearest
to the personnel decontamination facility and worked away from it. No asso-
ciation appeared to exist between the work direction and the location of the
HEPA-filtration units.
Final cleaning began with the spraying of walls, plastic critical con-
tainment barriers, and other surfaces with a water mist to remove any loosely
bound debris. The resultant asbestos-containing water on the floor was
gathered into pools by use of a rubber squeegee. The water was removed with
76
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a wet-vacuum that was not equipped with a HEPA filter. The water was con-
tainerized in double-layered, 6-mil-thick asbestos-disposal bags, which
usually contained plastic that had been removed from the walls and floors.
After the surfaces had dried, several workers conducted a visual inspec-
tion of pipe surfaces and wall-ceiling intersections to check for any resi-
dual material. If any material was found, the surface was wire-brushed. A
HEPA-filtered vacuum was then used to clean crevices around doors, windows,
floor-wall intersections, etc.
All of the vertical and horizontal surfaces were then wet-cleaned with
amended water containing a standard surfactant mixture plus a penetrating
encapsulant. The elevated horizontal and vertical surfaces were wiped first,
and then all other surfaces were wiped. All the surfaces except the floors
were wiped with cotton rags dampened with the amended water mixture. A
bucket of amended water was either used by a single worker or shared by
several workers. The workers did not appear to wipe the surfaces in any one
direction. The cloth rags were not replaced frequently, particularly during
the cleaning of elevated and hard-to-access surfaces. Nor was the amended
water changed frequently.
After the walls, windows, and other surfaces (shelves, ledges, plastic-
covered fixed objects, etc.) were wet-wiped, the floor was mopped with a
clean mop head that was wetted with amended water. No change in the water
was observed during this procedure.
Final cleaning involved one complete wet-mopping of floors. Aggressive
cleaning (i.e., air sweeping of all vertical and horizontal surfaces to
dislodge any remaining particulate) was not conducted.
Wastewater from the wet-wiping and mopping operations was treated as
asbestos-containing water and placed in double-layered 6-mil-thick standard
disposal bags. These standard asbestos disposal bags which contained
wastewater were not placed in leak-tight containers or solidified with a
gelling compound. The rags and mop heads used during cleaning also were
placed in these bags. The bags were not wet-wiped with amended water before
being removed from the abatement area.
Upon completing final cleaning, the abatement contractor requested a
final visual inspection by an onsite AST, who was the building owner's repre-
sentative. The AST conducted the visual inspection within 2 hours after
notification. The AST did not identify any areas that required further
cleaning.
FINAL VISUAL INSPECTION BY NEW JERSEY DEPARTMENT OF HEALTH, ASBESTOS CONTROL
SERVICE
The New Jersey Department of Health did not perform a visual inspection
at this site.
77
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AHERA CLEARANCE SAMPLING BY AST
The AHERA clearance sampling was initiated approximately 6 hours after
the site had passed the visual inspection. Using a hand-held electric leaf
blower, the AST conducted aggressive air sweeping of vertical and horizontal
surfaces for approximately 20 minutes, which is equivalent to approximately 5
minutes per 790 square feet of floor area. No floor fans were used subse-
quently to maintain air turbulence during sampling.
The clearance air samples were collected on 25-mm, 0.45-um pore size,
mixed cellulose ester membrane filters contained in a three-piece cassette
with a 50-mrn conductive cowl. The samples were collected at an approximate
flow rate of 10 liters per minute. The laboratory report indicated the
samples were analyzed in accordance with the AHERA mandatory TEM method.
Table D-3 presents the results of the clearance samples the AST col-
lected inside the abatement area. The samples met the initial AHERA clear-
ance criterion; i.e., an average asbestos concentration of less than 70
structures per square millimeter (s/mm2). The average asbestos concentration
for the five inside samples was 0 s/mm2.
Sample
Location
Inside
Inside
Inside
Inside
Inside
TABLE D-3. AHERA CLEARANCE
Sample volume,
liters
2477
2506
2554
2582
2592
SAMPLE RESULTS
Asbestos concentration
s/mm2 s/cm3
0 <0.002b
0 <0.002b
0 <0.002b
0 <0.002b
0 <0.002b
a Outside samples and blanks were not analyzed because the average
asbestos concentration for the five inside samples was less
than 70 s/nrnr.
Sensitivity of the analytical method.
78
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CASE HISTORY E
SITE DESCRIPTION
This abatement project involved removal of approximately 15,000 ft2 of
2-ft by 4-ft lay-in asbestos-containing acoustical ceiling tiles, and ap-
proximately 500 linear feet of mixed-diameter pipe insulation from a single-
story school building. The abatement area included corridors, classrooms,
offices, and recreational rooms.
The project specification indicated that the asbestos content of the
ceiling tiles was approximately 2 to 8 percent amosite, and that of the
thermal system insulation was 30 to 40 percent chrysotile.
VENTILATION AND NEGATIVE AIR PRESSURE
Twelve high-efficiency particulate air (HEPA) filtration units were
operated during the final cleaning period, and 10 were operated during AHERA
clearance sampling. Table E-l presents the measured air-intake volume for
each unit. The average air-intake volume was 1114 ft3/min during final
cleaning and 1348 ft3/min during AHERA clearance sampling. Based on the
volume of the work area (173,000 ft3) and the combined average air-intake
volumes, the air exchange rates were approximately 4.6 air changes per hour
during final cleaning and 5.6 air changes per hour during AHERA clearance
sampling.
Figures E-l and E-2 compare the measured air-intake volume of each
HEPA-filtration unit operating during final cleaning and AHERA clearance
sampling, respectively, with the unit's nominal airflow. The actual opera-
ting percentages of the nominal airflow ranged from 52 to 80 during final
cleaning and 65 to 87 during AHERA clearance sampling.
Table E-2 presents the static pressure differential measured across the
containment barriers at four locations. The number of locations tested was
determined by available access to the critical containment barriers. The
static pressure differential ranged from -0.01 to -0.02 in. water during
final cleaning and was -0.01 in. water during AHERA clearance sampling.
The asbestos safety technician (AST) did not monitor the static pressure
differential across the containment barrier. Instead, ventilation smoke
tubes were used to check negative pressure visually (i.e., direction of air-
flow through openings in the containment barrier, such as the decontamination
facility and waste load-out port). Reportedly, these qualitative checks were
performed each morning before the workshift and once during the workshift.
79
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TABLE E-l. AIRFLOW PERFORMANCE OF HEPA-FILTRATION UNITS
Airflow, ft /min
95% Confidence
interval
Model
1
1
2
2
2
2
2
2
3
3
3
3
1
1
2
2
2
2
2
3
3
3
Unit
1
2
3
4
5
6
7
8
9
10
11
12
1
2
3
4
5
6
7
8
9
10
Mean
1512
1601
1342
1015
1193
1193
1296
1273
701
739
732
772
AHERA
1722
1738
1577
1537
1262
1640
1583
813
795
818
Min.
Final
1176
1344
734
551
734
734
734
734
567
567
648
567
Max.
cleaning
2184
1848
1652
1468
1652
1468
1468
1652
810
851
851
891
dev.
224
156
222
237
225
215
220
220
47
76
62
78
Lower
1393
1518
1224
889
1073
1078
1179
1156
661
698
699
731
Upper
1631
1684
1460
1141
1312
1307
1413
1390
741
780
764
813
clearance sampling
1680
1512
1285
1101
734
1101
1285
729
648
729
1848
1848
1927
1835
1468
2019
1835
891
891
891
59
114
223
204
204
220
170
48
68
33
1690
1677
1458
1428
1153
1523
1492
787
758
800
1754
1798
1696
1645
1370
1757
1673
838
831
835
TABLE E-2. STATIC PRESSURE DIFFERENTIALS
ACROSS CONTAINMENT BARRIERS
(in. water)
Test location
1
2
3
4
Final cleaning
-0.01
-0.02
-0.01
-0.01
AHERA clearance
-0.01
-0.01
-0.01
-0.01
80
-------
oo
Percent of Nominal Airflow
100 -i
80-
60-
40
20-
76%
80%
69%
61% 61%
65%
52%
70%
74%
1 2 3 4 5 6 7 8 9 10 11 12
HEPA Filtration Unit
Model 1
Model 2
Model 3
Figure E-1. Airflow performance for HEPA filtration systems
operating during final cleanup.
-------
00
ro
Percent of Nominal Airflow
100 -r
so -
60
40
20
81% 79%
84%
65%
81%
86% 87%
81% 80% 82%
34567
HEPA F\\\ra\ioT) Unit
8
10
Model 1
Mode\ 2
Model 3
Figure E-2. Airflow performance for HEPA filtration systems
operating during AHERA clearance.
-------
The HEPA-filtration units were placed so that the makeup air entered the
work area through the personnel decontamination facility and waste load-out
port. The 11 operating units were positioned along exterior walls to facili-
tate venting of the exhaust through windows via an interconnected flexible
duct. The discharge air from the HEPA-filtration units was not monitored for
fiber content.
The contractor, who was responsible for maintaining the HEPA-filtration
units, stated that the prefilters, secondary filters, and HEPA filters were
changed before final cleaning was initiated. Thereafter, the prefilters were
changed when they became "visibly dirty," and the secondary filters were
changed about every 48 hours. The HEPA filters were changed every 500 to 700
hours (as recommended by the manufacturer) or when an audible alarm was
actuated by a differential pressure sensor set by the manufacturer.
FINAL CLEANING
Personal Protective Equipment
The personal protective equipment worn by the workers during final
cleaning consisted of full-body disposable coveralls and either full- or
half-facepiece air-purifying respirators equipped with dual-cartridge HEPA
filters.
Cleaning Procedures
Final cleaning began after the encapsulated plastic sheeting was removed
from the walls, floors, and other surfaces. The critical barriers, windows,
doors, student wall lockers, and heating, ventilation, and air-conditioning
(HVAC) vents remained sealed. The HEPA filtration units remained in service.
Final cleaning was organized so the workers began in the areas farthest
from the personnel decontamination facility and worked toward it. No as-
sociation appeared to exist between the work direction and the location of
HEPA-filtration units.
Final cleaning began with the wet-cleaning of all of vertical and hori-
zontal surfaces with amended water. The contractor reportedly prepared the
amended water solution by mixing approximately 1 ounce each of 50 percent
polyoxyethylene ester and 50 percent polyoxyethylene ether in 5 gallons of
water.
The T-bar grid network for the suspended ceiling tiles and vertical
surfaces were wiped first, followed by all the other surfaces. The surfaces,
excluding floors, were wiped with absorbent paper towels dampened with amend-
ed water. Each worker had a bucket of amended water to use. The workers did
not appear to wipe the vertical surfaces in any one direction. The paper
towels were not replaced frequently, especially during the cleaning of the
T-bar grid network. Nor was the amended water changed frequently.
83
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After the walls, windows, and other surfaces (shelves, ledges, counters,
plastic-covered HEPA-filtration systems and associated exhaust ducts, fixed
objects, etc.) were wet-wiped, the floor was mopped with a clean mop head
wetted with amended water. No change in water was observed during this
procedure.
Final cleaning involved one complete wet-mopping of floors. No aggres-
sive cleaning (i.e., air sweeping of all vertical and horizontal surfaces to
dislodge any remaining particulate) was conducted.
Wastewater from the wet-wiping and mopping operations was treated as
asbestos-containing water and placed in double-layered, 6-mil-thick, standard
disposal bags. These standard asbestos disposal bags which contained
wastewater were not placed in leak-tight containers or solidified with a
gelling compound. The paper towels and mop heads used during cleaning were
also placed in these bags. The bags were not wet-wiped with amended water
before being removed from the abatement area.
Upon completing final cleaning, the abatement contractor requested a
final visual inspection by an onsite AST, who was the building owner's
representative. The AST conducted the visual inspection within 2 hours after
notification. The AST did not identify any areas that required further
cleaning.
FINAL VISUAL INSPECTION BY NEW JERSEY DEPARTMENT OF HEALTH, ASBESTOS CONTROL
SERVICE
The New Jersey Department of Health did not perform a final visual
inspection at this site.
AHERA CLEARANCE SAMPLING BY AST
First Attempt
The AHERA clearance sampling was initiated approximately 24 hours after
the site had passed the visual inspection. Using a hand-held electric leaf
blower, the AST conducted aggressive air sweeping of vertical and horizontal
surfaces for approximately 30 minutes, which is equivalent to approximately 5
minutes per 3200 square feet of floor area. Six box-type floor fans with
18-inch blades were distributed throughout the abatement area and subsequent-
ly used to maintain air turbulence during sampling.
The clearance air samples were collected on 25-mm, 0.4-ym pore size,
polycarbonate membrane filters contained in a three-piece cassette with a
50-mm conductive cowl. The samples were collected at flow rates ranging from
9 to 10 liters per minute. The laboratory report indicated the samples were
analyzed in accordance with the AHERA mandatory TEM method.
Table E-3 presents the results of clearance samples the AST collected
inside the abatement area. The samples did not meet the initial AHERA
84
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clearance criterion of an average asbestos concentration of less than 70
structures per square millimeter (s/mm2); the mean asbestos concentration in
the inside samples was actually 156 s/mm2. The AST did not analyze the five
samples collected outside of the abatement area; thus, the Z-test comparison
was not conducted.
TABLE E-3. AHERA CLEARANCE SAMPLE RESULTS—FIRST ATTEMPT
Asbestos concentration
Sample
location
Inside
Inside
Inside
Inside
Inside
Sample volume,
liters
2851
2870
2890
2851
2860
s/mm2
312
31
250
125
62
s/cm3
0.042
0.004
0.034
0.017
0.008
Outside samples and blanks were not analyzed.
Before recleaning of the site was begun, all surfaces, particularly the
T-bar grid network, were swept with a 1-horsepower leaf blower for approxi-
mately 60 minutes. Recleaning of the site was initiated approximately 16
hours later. The site was then cleaned by the same procedures used during
the first cleaning, except that the T-bar grid network was thoroughly cleaned
with a HEPA-filtered vacuum prior to the wet-cleaning with amended water.
Hard-to-reach areas, including floor-wall intersections and crevices around
doors, were cleaned with a HEPA-filtered vacuum.
Second Attempt
The AHERA clearance sampling was initiated approximately 28 hours after
the site had passed the visual inspection. Using a hand-held electric leaf
blower, the AST conducted aggressive air sweeping of vertical and horizontal
surfaces for approximately 15 minutes, which is equivalent to approximately 5
minutes per 6400 square feet of floor area or 5 minutes per 58,000 cubic feet
of work space. Six box-type floor fans with 18-inch blades were distributed
throughout the abatement area and subsequently used to maintain air turbu-
lence during sampling.
The clearance air samples were collected on 25-mm, 0.4-ym pore size,
polycarbonate membrane filters contained in a three-piece cassette with a
50-mrn conductive cowl. The samples were collected at flow rates ranging from
9 to 10 liters per minute. The laboratory report indicated that the samples
were analyzed in accordance with the AHERA mandatory TEM method.
Table E-4 presents the results of the AST's clearance samples collected
inside the abatement area. The samples met the initial AHERA clearance
criterion by having an asbestos concentration of less than 70 s/mm2. The
average asbestos concentration for the five inside samples was 26 s/mm2.
85
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TABLE E-4. AHERA CLEARANCE SAMPLE RESULTS—SECOND ATTEMPT
Sample
location
Inside
Inside
Inside
Inside
Inside
Sample volume,
liters
2264
2310
2277
2287
2264
Asbestos
s/mm2
26
26
0
0
0
concentration
s/cm3
0.004
0.004
0.004b
0.004b
0.004b
Outside samples and blanks were not analyzed because the average
asbestos concentration for the five inside samples was less than
70 s/mm2.
Sensitivity of the analytical method.
86
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CASE HISTORY F
SITE DESCRIPTION
This abatement project involved removal of approximately 2200 ft2 of
thermal system insulation from a single-story school building. The abatement
involved removal of asbestos-containing thermal insulation materials on
mechanical equipment (i.e., boilers, boiler breeching, and pipes). The
project specification indicated that the asbestos content of the thermal
insulation was approximately 30 to 40 percent chrysotile.
VENTILATION AND NEGATIVE AIR PRESSURE
One high-efficiency particulate air (HEPA) filtration unit was operated
during the final cleaning period, and one was operated during AHERA clearance
sampling. Table F-l presents the measured air-intake volume for each unit.
The average air-intake volume was 1428 ft3/min during final cleaning and
1428 ft3/min during AHERA clearance sampling. Based on the volume of the
work area (6674 ft3) and the average air-intake volumes, the air exchange
rates were approximately 12.8 air changes per hour during final cleaning and
12.8 air changes per hour during AHERA clearance sampling.
TABLE F-l. AIRFLOW PERFORMANCE OF HEPA-FILTRATION UNITS
, 95% Confidence
Airflow, ft /min interval
Std.
Model Unit Mean Min. Max. dev. Lower Upper
Final cleaning
1 1 1428 1008 1848 307 1264 1592
AHERA clearance sampling
1 1 1428 1008 1848 277 1280 1576
Figure F-l compares the measured air-intake volume for each HEPA-
filtration unit operating during final cleaning and AHERA clearance sampling,
with the unit's nominal air flow.
87
-------
Percent of Nominal Airflow
100
80
60
40
20
71%
71%
Final
AHERA
I
Figure F-1. Airflow performance for HEPA filtration systems
operating during final cleanup and AHERA clearance.
-------
Table F-2 presents the static pressure differential measured across the
containment barriers at one location. The number of locations tested was
determined by available access to the critical containment barriers. The
static pressure differential was -0.02 in. water during final cleaning and
-0.02 in. water during AHERA clearance sampling.
TABLE F-2. STATIC PRESSURE DIFFERENTIALS
ACROSS CONTAINMENT BARRIERS
(in. water)
Test location Final cleaning AHERA clearance
1 -0.02 -0.02
The asbestos safety technician (AST) did not monitor the static pressure
differential across the containment barrier. Instead, ventilation smoke
tubes were used to check the negative pressure visually (i.e., direction of
airflow through openings in the containment barrier, such as the decontamina-
tion facility and waste load-out port). Reportedly, these qualitative checks
were performed twice during a workshift, once in the morning, and once in the
afternoon.
The HEPA-filtration unit was placed so that the makeup air entered the
work area through the personnel decontamination facility and waste load-out
port. The operating unit was positioned along an exterior wall to facilitate
venting of the exhaust through a window via an interconnected flexible duct.
The discharge air from the HEPA-filtration units was not monitored for fiber
content.
The contractor, who was responsible for maintaining the HEPA-filtration
units, stated that the prefilters, secondary filters, and HEPA filters were
changed before final cleaning was initiated. Thereafter, the prefilters and
secondary filters were changed when they became "visibly dirty." The HEPA
filters were changed every 600 to 700 hours (as recommended by the manufac-
turer) or when an audible alarm was actuated by a differential pressure
sensor set by the manufacturer.
FINAL CLEANING
Personal Protective Equipment
The personal protective equipment worn by the workers during final
cleaning consisted of full-body disposable coveralls and either full- or
half-facepiece air-purifying respirators equipped with dual-cartridge HEPA
filters.
89
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Cleaning Procedures
Final cleaning began after the plastic sheeting was removed from the
walls, floors, and other surfaces. The critical barriers, windows, doors,
and heating, ventilation, and air-conditioning (HVAC) vents remained sealed.
The HEPA-air filtration units remained in service.
Final cleaning was organized so the workers began in the areas farthest
from the personnel decontamination facility and worked toward it. No as-
sociation appeared to exist between the work direction and the location of
the HEPA-filtration units.
Final cleaning began with the spraying of walls, plastic critical con-
tainment barriers, and other surfaces with water to remove any loosely bound
debris. The resultant asbestos-containing water on the floor was gathered
into pools by use of a rubber squeegee. The bulk of the pooled water was
scooped up with plastic-bladed shovels. The water was containerized in
double-layered, 6-mil-thick, asbestos-disposal bags, which usually contained
plastic that had been removed from the walls and floors. The residual water
removed with a wet vacuum was also placed in these bags.
All of the vertical and horizontal surfaces were then wet-cleaned with
amended water. The contractor reportedly prepared the amended water solution
by mixing approximately 1 ounce each of 50 percent polyoxyethylene ester and
50 percent polyoxyethylene ether in 5 gallons of water.
The elevated horizontal and vertical surfaces were wiped first, followed
by all the other surfaces. All of the surfaces except the floors were wiped
with paper towels dampened with amended water. A bucket of amended water was
either used by a single worker or shared by several workers. The workers did
not appear to wipe the surfaces in any one direction. The paper towels were
not replaced frequently, especially during the cleaning of elevated and
hard-to-access surfaces. Nor was the amended water changed frequently.
After the walls, windows, and other surfaces were wet-wiped, the floor
was mopped with a clean mop head wetted with amended water. No changes in
the water was observed during this procedure.
No aggressive cleaning (i.e., air sweeping of all vertical and hori-
zontal surfaces to dislodge any remaining particulate) was conducted.
Wastewater from the wet-wiping and mopping operations was treated as
asbestos-containing water and placed in double-layered, 6-mil-thick, standard
disposal bags. These standard asbestos disposal bags which contained
wastewater were not placed in leak-tight containers or solidified with a
gelling compound. The paper towels and mop heads used during cleaning also
were placed in these bags. The bags were not wet-wiped with amended water
before being removed from the abatement area.
Upon completing final cleaning, the abatement contractor requested a
final visual inspection by an onsite AST, who was the building owner's
90
-------
representative. The AST conducted the visual inspection within 1 hour after
notification. The AST identified the following areas that required further
cleaning: 1) debris in recessed areas on the side of the boiler, and 2)
debris around valves. After these areas were recleaned, the AST conducted a
final walk-through inspection to assure that the identified areas were clean.
FINAL VISUAL INSPECTION BY NEW JERSEY DEPARTMENT OF HEALTH, ASBESTOS CONTROL
SERVICE
The New Jersey Department of Health did not perform a final visual
inspection at this site.
AHERA CLEARANCE SAMPLING
The AHERA clearance sampling was initiated approximately 18 hours after
the site passed the visual inspection conducted by the AST. Using a hand-
held electric leaf blower, the AST conducted aggressive air sweeping of
vertical and horizontal surfaces for approximately 4 minutes, which is
equivalent to approximately 5 minutes per 700 ft2 of floor area. One
box-type floor fan with 18-inch blades was subsequently used to maintain air
turbulence during sampling. Because this abatement project involved the
removal of less than 3000 ft2 of asbestos-containing material, AHERA allows
the use of Phase Contrast Microscopy (PCM) to analyze the air samples col-
lected to clear the site. The AST collected only one sample inside the work
area for clearance purposes. This practice is not in accordance with the
AHERA clearance protocol, i.e., five samples must be collected inside the
abatement area and each must have a fiber concentration of less than or equal
to 0.01 f/cm3 of air to pass the clearance test. This sample consisted of a
25-mm, 0.4-pm pore size, polycarbonate membrane filter contained in a three-
piece cassette with a 50-mm conductive cowl. The sample was collected at a
flow rate of approximately 10 liters per minute. The laboratory report
indicates that the samples were analyzed in accordance with the NIOSH Method 7400,
which uses PCM.
Table F-3 presents the results of the AST's clearance sample collected
inside the abatement area. The asbestos concentration for this sample was
less than the AHERA limit of 0.01 fiber per cubic centimeter.
TABLE F-3. AHERA CLEARANCE SAMPLE RESULTS
Asbestos concentration
Sample Sample volume,
location liters f/mm2 f/cm3
Inside 2000 19 0.004
91
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CASE HISTORY G
SITE DESCRIPTION
This abatement project involved removal of asbestos-containing thermal
insulation materials on mechanical equipment (i.e., boiler lagging, boiler
breeching, and boiler gasket) in a two-story school building. The project
specification indicated that asbestos content of the boiler lagging was
approximately 10 to 15 percent chrysotile and 35 to 40 percent amosite; the
asbestos content of the boiler breeching was 25 to 30 percent chrysotile and
30 to 35 percent amosite; and the asbestos content of the boiler gasket was
70 to 75 percent chrysotile. The project specification did not quantify the
amount of asbestos-containing material in each location.
VENTILATION AND NEGATIVE AIR PRESSURE
Two high-efficiency particulate air (HEPA) filtration units were oper-
ated during the final cleaning period, and two were operated during AHERA
clearance sampling. Table G-l presents the measured air-intake volume for
each unit. The average air-intake volume was 1713 ft3/min during final
cleaning and 1681 ft3/min during AHERA clearance sampling. Based on the
volume of the work area (23,000 ft3) and the combined average air-intake
volumes, the air exchange rates were approximately 8.9 air changes per hour
during final cleaning and 8.7 air changes per hour during AHERA clearance
sampling.
TABLE 6-1. AIRFLOW PERFORMANCE OF HEPA-FILTRATION UNITS
- 95% Confidence
Airflow, ft /min interval
Model
Unit
Mean
Min.
Max.
3 LU .
dev.
Lower
Upper
Final cleaning
1
1
1
2
1475
1950
1400
1800
1600
2200
97
112
1423
1890
1527
2010
AHERA clearance sampling
1 1 1575 1400 1800 97 1523 1627
1 2 1788 1600 2000 111 1728 1847
92
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Figures 6-1 and G-2 compare the measured air-intake volume for each
HEPA-filtration unit operating during final cleaning and AHERA clearance
sampling, respectively, with the unit's nominal airflow. The actual operat-
ing percentages of the nominal air flow were 74 and 98 during final cleaning
and 79 and 89 during AHERA clearance sampling. The reason for the signifi-
cantly higher operating airflow performance of the second air filtration unit
is not known.
Table G-2 presents the static pressure differential measured across the
containment barriers at one location. The number of locations tested was
determined by available access to the critical containment barriers. The
static pressure differential was -0.01 in. water during final cleaning and
-0.01 in. water during AHERA clearance sampling.
TABLE G-2. STATIC PRESSURE DIFFERENTIALS
ACROSS CONTAINMENT BARRIERS
(in. water)
Test location Final cleaning AHERA clearance
1 -0.01 -0.01
The asbestos safety technician (AST) did not monitor the static pressure
differential across the containment barriers. Instead, ventilation smoke
tubes were used to check the negative pressure visually (i.e., direction of
airflow through openings in the containment barrier, such as the decontamina-
tion facility and waste load-out port). Reportedly, these qualitative checks
were performed each morning.
The HEPA-filtration units were placed so that the makeup air entered the
work area through the personnel decontamination facility and waste load-out
port. The two operating units were positioned along exterior walls to faci-
litate venting of the exhaust through windows via an interconnected flexible
duct. The discharge air from the HEPA-filtration units was not monitored for
fiber content.
The contractor, who was responsible for maintaining the HEPA-filtration
units, stated that the prefilters and secondary filters were changed before
final cleaning was initiated. The HEPA filters were changed at the beginning
of the project. Thereafter, the prefilters were changed daily and the sec-
ondary filters were changed when they became "visibly dirty." The HEPA
filters were changed every 600 to 700 hours (as recommended by the manu-
facturer) or when an audible alarm was actuated by a differential pressure
sensor set by the manufacturer.
93
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Percent of Nominal Airflow
100
80
60
40
20
74%
98%
7
HEPA Filtration Unit
(Same Model)
Figure G-1. Airflow performance for HEPA filtration systems
operating during final cleanup.
-------
Percent of Nominal Airflow
100
80
60
40
20
89%
79%
/ /
HEPA Filtration Unit
(Same Model)
Figure G-2. Airflow performance for HEPA filtration systems
operating during AHERA clearance.
-------
FINAL CLEANING
Personal Protective Equipment
The personal protective equipment worn by the workers during final
cleaning consisted of full-body disposable coveralls, and either full- or
half-facepiece air-purifying respirators equipped with dual-cartridge HEPA
efficiency particulate air filters.
Cleaning Procedures
Final cleaning began after the encapsulated plastic sheeting was removed
from the walls, floors, and other surfaces. The windows, doors, stationary
objects, and heating, ventilation, and air-conditioning (HVAC) vents remained
sealed. The HEPA filtration units remained in service.
Final cleaning began with the brushing of abated surfaces to remove any
visible debris on the substrate. A vacuum equipped with a HEPA filter was
then used to clean these surfaces and other areas, including crevices around
electrical outlets, floor-wall intersections, etc. All of the vertical and
horizontal surfaces were then sprayed with water. The bulk of the pooled
water was scooped up with plastic-bladed shovels, which worked surprisingly
well. The water was containerized in double-layered, 6-mil-thick, asbestos-
disposal bags, which usually contained plastic that had been removed from the
walls and floors. The residual water removed with a wet vacuum also was
placed in these bags.
All of the vertical and horizontal surfaces were then wet-cleaned with
amended water. The contractor reportedly prepared the amended water solution
by mixing approximately 2 ounces each of 50 percent polyoxyethylene ester and
50 percent polyoxyethylene ether in 5 gallons of water.
The elevated horizontal and vertical surfaces were wiped first, and then
all other surfaces. All the surfaces except the floors were wiped with
cotton rags dampened with amended water. A bucket of amended water was
either used by a single worker or shared by several workers. The workers did
not appear to wipe the surfaces in any one direction. The cloth rags were
not replaced frequently, particularly during the cleaning of elevated and
hard-to-access surfaces. Nor was the amended water changed frequently.
After the surfaces were wet-wiped, the floor was mopped with a clean mop
head wetted with amended water. No change in the water was observed during
this procedure.
Final cleaning involved one complete wet-cleaning of the floors. No
aggressive cleaning (i.e., air sweeping of all vertical and horizontal sur-
faces to dislodge any remaining particulate) was conducted.
Wastewater from the wet-wiping and mopping operations was treated as
asbestos-containing water and placed in double-layered, 6-mil-thick, standard
disposal bags. These standard asbestos disposal bags which contained
wastewater were not placed in leak-tight containers or solidified with a
96
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gelling compound. The rags and mop heads used during cleaning also were
placed in these bags. The bags were not wet-wiped with amended water before
being removed from the abatement area.
Upon completing final cleaning, the abatement contractor requested a
final visual inspection by an onsite AST, who was the building owner's
representative. The AST conducted a visual inspection within 1 hour after
notification. The AST identified the presence of debris on several pipe
valves. After the designated areas were recleaned, the AST conducted a final
walk-through inspection assure that the identified areas were clean.
FINAL VISUAL INSPECTION BY NEW JERSEY DEPARTMENT OF HEALTH, ASBESTOS CONTROL
SERVICE
The New Jersey Department of Health did not perform a visual inspection
of this site.
AHERA CLEARANCE SAMPLING BY AST
First Attempt
The AHERA clearance sampling was initiated approximately 2 hours after
the site had passed a visual inspection conducted by the AST. The AST did
not conduct aggressive air sweeping of vertical and horizontal surfaces;
however, two box-type floor fans with 18-inch blades were used to create air
turbulence during the sampling.
The clearance air samples were collected on 25-mm, 0.4-um pore size,
polycarbonate membrane filters contained in a three-piece cassette with a
50-mm conductive cowl. The AST stated that the polycarbonate filters were
checked for background asbestos contamination prior to sampling. The samples
were collected at flow rates ranging from 9 to 10 liters per minute. The
laboratory report indicates that the samples were analyzed in accordance with
the AHERA mandatory TEM method.
Table G-3 presents the results of the AST's clearance samples collected
inside the abatement area. The samples did not pass the initial AHERA clear-
ance criterion of less than 70 structures per square millimeter (s/mm2). The
actual mean asbestos concentration for the inside samples was 279 s/mm2;
therefore, the five outside samples (4 in the perimeter of the abatement area
and one outdoors) and three field blanks were analyzed. The AHERA z-test was
used to compare the five inside samples and five outside samples. Because
the calculated Z statistic (1.76) was greater than the AHERA limit of 1.65,
recleaning was required.
The recleaning included a general wet-cleaning of most surfaces with
cotton rags dampened with amended water, limited vacuuming of crevices, and
wet-mopping of the floor with amended water.
97
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TABLE G-3. AHERA CLEARANCE SAMPLE RESULTS—FIRST ATTEMPT
Asbestos concentration
Sample
location
Inside
Inside
Inside
Inside
Inside
Outside
Outside
Outside
Outside
Outside
Blank
Blank
Blank
Sample volume,
liters
1852
1823
1809
1822
1820
1854
1834
1820
1847
1847
_
-
-
s/mm2
386
186
253
372
200
190
204
70
54
109
53
40
67
s/cm3
0.074
0.036
0.058
0.072
0.038
0.037
0.039
0.013
0.010
0.020
—
-
-
Second Attempt
The AHERA clearance sampling was initiated approximately 3 hours after
the site had passed the AST's visual inspection. The AST did not conduct
aggressive air sweeping of vertical and horizontal surfaces; however, two
box-type floor fans with 18-inch blades were used to create air turbulence
during sampling.
The AST collected the same number of samples and used the same sampling
and analytical methodology as during the first clearance attempt.
Table G-4 presents the results of the clearance samples the AST col-
lected inside the abatement area. The samples did not pass the initial AHERA
clearance criterion of 70 s/mm2; the mean asbestos concentration for the
inside samples was actually 250 s/mm2. The AST did not analyze the five
samples collected outside the abatement area; therefore, the Z-test compari-
son was not conducted.
Failing the AHERA clearance a second time resulted in a thorough re-
cleaning of the site. This included vacuuming of all abated surfaces, floor-
wall intersections, areas along electrical conduits and outlets, valves, etc.
The vacuuming was followed by a complete spraying of all vertical and hori-
zontal surfaces with water and a wet cleaning with cotton rags dampened with
amended water.
98
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TABLE G-4. AHERA CLEARANCE SAMPLE RESULTS-SECOND ATTEMPT
Sample
location
Inside
Inside
Inside
Inside
Inside
Blank
Blank
Blank
Sample volume,
liters
1852
1823
1809
1822
1820
—
_
-
Asbestos concentration
s/mm2
203
44
334
378
291
149
60
104
s/cm3
0.039
0.008
0.077
0.073
0.067
—
_
-
a Outside samples were not analyzed.
Third Attempt
The AHERA clearance sampling was initiated approximately one hour after
the site passed the AST's visual inspection. The AST did not conduct ag-
gressive air sweeping of vertical and horizontal surfaces; however, two
box-type floor fans with 18-inch blades were used to create air turbulence
during sampling.
The AST collected the same number of samples and used the same sampling
and analytical methodology as in the first and second clearance attempts.
Table G-5 presents the results of the AST's clearance samples collected
inside the abatement area. The samples passed the AHERA prescreening clear-
ance criterion (i.e., an average asbestos concentration of less than
70 s/mm2); the average asbestos concentration for the five inside samples was
46 s/mm2.
99
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TABLE G-5. AHERA CLEARANCE SAMPLE RESULTS-THIRD ATTEMPT
Sample
location
Inside
Inside
Inside
Inside
Inside
Sample volume,
liters
1732
1699
1743
1743
1690
Asbestos concentration
s/mm2
53
35
35
70
35
s/cm3
0.012
0.008
0.008
0.016
0.008
Outside samples and blanks were not analyzed because average
asbestos concentration for the five inside samples was less
than 70 s/mm2.
100
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CASE HISTORY H
SITE DESCRIPTION
This abatement project involved removal of asbestos-containing acous-
tical ceiling plaster, spray-applied fireproofing, and mixed diameter pipe
insulation from a single-story school building. The abatement area included
corridors, adjacent vestibules, classrooms, offices, and recreational rooms.
The project specification stated that the removal involved approximately
1600 ft2 of fireproofing containing 25 to 50 percent chrysotile, approxi-
mately 21,000 ft2 of acoustical plaster containing 10 to 25 percent chryso-
tile, and approximately 100 linear feet of air-cell-paper insulation
containing 40 to 60 percent chrysotile.
VENTILATION AND NEGATIVE AIR PRESSURE
Five high-efficiency particulate air (HEPA) filtration units were oper-
ated during the final cleaning period, and five were operated during AHERA
clearance sampling. Table H-l presents the measured air-intake volume of
each unit. The average air-intake volume was 1487 ft3/min during final
cleaning and 1400 ft3/min during AHERA clearance sampling. Based on the
volume of the work area (95,500 ft3) and the combined average air-intake
volumes, the air exchange rates were approximately 4.7 air changes per hour
during final cleaning and 4.4 air changes per hour during AHERA clearance
sampling.
Figures H-l and H-2 compare the measured air-intake volume of each
HEPA-filtration unit operating during final cleaning and AHERA clearance
sampling, respectively, with the unit's nominal airflow. The actual operat-
ing percentages of the nominal airflow ranged from 67 to 83 during final
cleaning and from 65 to 72 during AHERA clearance sampling.
Table H-2 presents the static pressure differential measured across the
containment barriers at four locations. The number of locations tested was
determined by available access to the critical containment barriers. The
static pressure differential ranged from -0.01 to -0.02 in. water during
final cleaning and - 0.01 to -0.02 in. water during AHERA clearance sampling.
The increased differential pressure is most likely attributable to the addi-
tional number of HEPA-filtration units that were operating.
The asbestos safety technician (AST) did not monitor the static pressure
differential across the containment barrier. Instead, ventilation smoke
tubes were used to check the negative pressure visually (i.e., direction of
101
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Percent of Nominal Airflow
100 -
80 -
60 -
234
HEPA Filtration Unit
Model 1
Model 2
Figure H-1. Airflow performance for HEPA filtration systems
operating during final cleanup.
-------
Percent of Nominal Airflow
o
GO
100 -i
234
HEPA Filtration Unit
Model 1
Model 2
Figure H-2. Airflow performance for HEPA filtration systems
operating during AHERA clearance.
-------
TABLE H-l. AIRFLOW PERFORMANCE OF HEPA-FILTRATION UNITS
3
Airflow, ft /min
Model
1
1
1
2
2
Unit
1
2
3
4
5
Mean
1661
1547
1475
1344
1410
Min.
Final
1344
1344
1176
840
1008
Max.
Std.
dev.
95% Confidence
interval
Lower
Upper
cleaning
1848
1680
1764
1680
1596
AHERA clearance
1
1
1
2
2
1
2
3
4
5
1370
1465
1444
1302
1418
1176
1344
1344
840
1260
1512
1680
1680
1680
1680
136
104
129
272
151
sampling
93
111
99
269
102
1589
1491
1406
1197
1330
1321
1406
1391
1159
1363
1733
1602
1544
1489
1491
1420
1524
1497'
1445
1472
TABLE H-2. STATIC PRESSURE DIFFERENTIALS
ACROSS CONTAINMENT BARRIERS
(in. water)
Test location
Final cleaning AHERA clearance
1
2
3
4
-0.01
-0.01
-0.01
-0.02
-0.02
-0.01
-0.01
-0.02
104
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airflow through openings in the containment barrier, such as the decontamina-
tion facility). Reportedly, these qualitative checks were performed once in
the morning and once in the afternoon.
The HEPA-filtration units were placed so that the makeup air entered the
work area through the personnel decontamination facility and waste load-out
port. Four of the five operating units were positioned along exterior walls
to facilitate venting of the exhaust through windows via an interconnected
flexible duct. The exhaust of the fifth unit was vented through a doorway
via an interconnected flexible duct that passed through an area outside of
the abatement area. The discharge air from the HEPA-filtration units was not
monitored for fiber content.
The contractor, who was responsible for maintaining the HEPA-filtration
units, stated that the prefilters, secondary filters, and HEPA filters were
changed before final cleaning was initiated. Thereafter, the prefilters were
changed daily and the secondary filters were changed when they became "visi-
bly dirty." The HEPA filters were changed every 600 to 700 hours (as recom-
mended by the manufacturer) or when an audible alarm was actuated by a dif-
ferential pressure sensor set by the manufacturer.
FINAL CLEANING
Personal Protective Equipment
The personal protective equipment worn by the workers during final
cleaning consisted of full-body disposable coveralls and either full- or
half-facepiece air-purifying respirators equipped with dual-cartridge HEPA
filters.
Cleaning Procedures
Final cleaning began after the plastic sheeting was removed from the
walls, floors, and other surfaces. The critical barriers, windows, doors,
stationary objects, and heating, ventilation, and air-conditioning (HVAC)
vents remained sealed. The HEPA filtration units remained in service.
Final cleaning was organized so the workers began in the areas nearest
to the personnel decontamination facility and worked away from it. No as-
sociation appeared to exist between the work direction and the location of
HEPA-filtration units.
Final cleaning began with the spraying of walls, plastic critical con-
tainment barriers, and other vertical surfaces with a water mist to remove
any loosely bound debris. The resultant asbestos-containing water on the
floor was gathered into pools by use of a rubber squeegee. The bulk of the
pooled water was scooped up with plastic-bladed shovels. The water was
containerized in double-layered, 6-mil-thick, asbestos-disposal bags, which
usually contained plastic that had been removed from the walls and floors.
The residual water removed with a wet vacuum was also placed in these bags.
105
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After the surfaces had dried, a vacuum equipped with a HEPA filter was
used to clean crevices around windows, doors, and shelves; floor-wall inter-
faces; etc.
All of the vertical and horizontal surfaces were then wet-cleaned with
amended water. The contractor reportedly prepared the amended water solution
by mixing approximately 1 ounce each of 50 percent polyoxyethylene ester and
50 percent polyoxyethylene ether in 5 gallons of water.
The elevated horizontal and vertical surfaces were wiped first and then
all other surfaces. All surfaces, except the floors, were wiped with absor-
bent paper towels dampened with amended water. The contractor stated that
cotton rags were not used because their repeated use increases the potential
of smearing residual particulates on the surfaces being cleaned. A bucket of
amended water was either used by a single worker or shared by several work-
ers. The workers did not appear to wipe the surfaces in any one direction.
The paper towels were not replaced frequently, particularly during the clean-
ing of elevated and hard-to-access surfaces. Nor was the amended water
changed frequently.
After the walls and other surfaces had been wet-wiped, the floor was
mopped with a clean mop head wetted with amended water. No change of the
water was observed during this procedure.
Final cleaning involved one complete wet-mopping of floors with a clean
mop head and amended water. No aggressive cleaning (i.e., air sweeping of
all vertical and horizontal surfaces to dislodge any remaining particulate)
was conducted.
Wastewater from the wet-wiping and mopping operations was treated as
asbestos-containing water and placed in double-layered, 6-mil-thick, standard
disposal bags. These standard asbestos disposal bags which contained
wastewater were not placed in leak-tight containers or solidified with a
gelling compound. The paper towels and mop heads used during cleaning also
were placed in these bags. The bags were not wet-wiped with amended water
before being removed from the abatement area.
Upon completing final cleaning, the abatement contractor requested a
final visual inspection by an (AST, who was the building owner's represen-
tative. The AST conducted a visual inspection within 2 hours after noti-
fication. The AST identified several areas, especially elevated horizontal
surfaces (including the tops of pipes and ventilation ducts), that required
further cleaning. After these designated areas were recleaned, the AST
conducted a final walk-through inspection to assure that the identified areas
were clean.
FINAL VISUAL INSPECTION BY NEW JERSEY DEPARTMENT OF HEALTH, ASBESTOS CONTROL
SERVICE
The site failed the first visual inspection because of the presence of
debris 1) on heating units, 2) on pipes in the hallways and classrooms, 3) on
106
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electrical wires and outlet boxes, 4) at floor-wall corners, and 5) around
air vents. These things were corrected, and the site passed the second
visual inspection.
AHERA CLEARANCE SAMPLING BY AST
The AHERA clearance sampling was initiated approximately 24 hours after
the site passed the visual inspection. Using a hand-held electric leaf
blower, the AST conducted aggressive air sweeping of vertical and horizontal
surfaces for approximately 30 minutes, which is equivalent to approximately 5
minutes per 1000 square feet of floor area. No floor fans were used subse-
quently to maintain air turbulence during sampling.
The clearance air samples were collected on 25-mm, 0.45-ym pore size,
mixed cellulose ester membrane filters contained in a three-piece cassette
with a 50-mrn conductive cowl. The samples were collected at flow rates of
approximately 10 liters per minute. The laboratory report indicates that
the samples were analyzed in accordance with the AHERA mandatory TEM method.
Table H-3 presents the results of the AST's clearance samples collected
inside the abatement area. The samples met the initial AHERA clearance
criterion by having an asbestos concentration less than 70 structures per
square millimeter (s/mm2). The average asbestos concentration for the seven
inside samples was 4 s/mm2.
TABLE H-3. AHERA CLEARANCE SAMPLE RESULTS
Asbestos concentration
Sample Sample volume,
location liters s/mm2 s/cm3
Inside
Inside
Inside
Inside
Inside
Inside
Inside
2000
2008
2000
2024
2000
2080
2064
0
0
25
0
0
0
0
-------
CASE HISTORY I
SITE DESCRIPTION
This abatement project involved removal of approximately 5100 ft2 of
spray-applied, asbestos-containing, acoustical ceiling plaster from a single-
story school building. The abatement area included corridors, classrooms,
offices, a lobby, and an auditorium. The project specification indicated
that the asbestos content of the ceiling plaster was approximately 5 to 25
percent chrysotile.
VENTILATION AND NEGATIVE AIR PRESSURE
Four high-efficiency particulate air (HEPA) filtration units were oper-
ated during the final cleaning period, and four were operated during AHERA
clearance sampling. Table 1-1 presents the measured air-intake volume for
each unit. The average air-intake volume was 991 ft3/min during final clean-
ing and 1013 ft3/min during AHERA clearance sampling. Based on the volume of
the work area (40,000 ft3) and the combined average air-intake volumes, the
air-exchange rates were approximately 5.9 air changes per hour during final
cleaning and 6.1 air changes per hour during AHERA clearance sampling.
Figures 1-1 and 1-2 compare the measured air-intake volume for each
HEPA-filtration unit operating during final cleaning and AHERA clearance
sampling, respectively, with the unit's nominal airflow. The actual operat-
ing percentages of the nominal air flow ranged from 46 to 57 during final
cleaning and from 47 to 53 during AHERA clearance sampling.
Table 1-2 presents the static pressure differential measured across the
containment barriers at three locations. The number of locations tested was
determined by available access to the critical containment barriers. The
static pressure differential ranged from -0.02 to -0.03 in. water during both
final cleaning and AHERA clearance sampling.
The asbestos safety technician (AST) did not monitor the static pressure
differential across the containment barriers. Instead, ventilation smoke
tubes were used to check the negative pressure (i.e., direction of airflow
through openings in the containment barrier, such as the decontamination
facility and waste load-out port). Reportedly, these qualitative checks were
performed each morning.
The HEPA-filtration units were placed so that the makeup air entered the
work area through the personnel decontamination facility and waste load-out
108
-------
TABLE 1-1. AIRFLOW PERFORMANCE OF HEPA-FILTRATION UNITS
Airflow, ft /min
Model Unit Mean Min.
Max.
Std.
dev.
95% Confidence
interval
Lower Upper
Final cleaning
1
1
1
1
1
2
3
4
943
1135
913
974
756
941
864
864
1176
1344
1021
1099
108
147
61
76
886
1057
880
933
1000
1213
945
1015
AHERA clearance sampling
1
1
1
1
1
2
3
4
1055
1053
937
1008
924
941
864
903
1176
1176
1021
1099
78
79
48
58
1013
1011
912
977
1097
1095
963
1039
TABLE 1-2. STATIC PRESSURE DIFFERENTIALS
ACROSS CONTAINMENT BARRIERS
(in. water)
Test location
Final cleaning
AHERA clearance
1
2
3
-0.02
-0.02
-0.03
-0.03
-0.02
-0.02
109
-------
Percent of Nominal Airflow
100
80
60
40
20
47%
57%
46%
49%
7
1234
HEPA Filtration Unit
(Same Model)
Figure 1-1. Airflow performance for HEPA filtration systems
operating during final cleanup.
-------
Percent of Nominal Airflow
100
80
60
40
20
53%
53%
47%
50%
1234
HEPA Filtration Unit
(Same Model)
Figure I-2. Airflow performance for HEPA filtration systems
operating during AHERA clearance.
-------
port. The four operating units were positioned along exterior walls to
facilitate venting of the exhaust through windows via an interconnected
flexible duct. The discharge air from the HEPA-filtration units was not
monitored for fiber content.
The contractor, who was responsible for maintaining the HEPA-filtration
units, stated that the prefilters, secondary filters, and HEPA filters were
changed before final cleaning was initiated. Thereafter, the prefilters were
changed when they became "visibly dirty," and the secondary filters were
changed after each workshift. The HEPA filters were changed every 900 to
1000 hours or when an audible alarm was actuated by a differential pressure
sensor set by the manufacturer.
FINAL CLEANING
Personal Protective Equipment
The personal protective equipment worn by the workers during final
cleaning consisted of full-body disposable coveralls and either full- or
half-facepiece air-purifying respirators equipped with dual-cartridge HEPA
filters.
Cleaning Procedures
Final cleaning began after the encapsulated plastic sheeting was removed
from the walls, floors, light fixtures, and other surfaces. The windows,
doors, and heating, ventilation, and air-conditioning (HVAC) vents remained
sealed. The HEPA filtration units remained in service.
Final cleaning was organized so the workers began in the areas farthest
from the personnel decontamination facility and worked toward it. No as-
sociation appeared to exist between the work direction and location of HEPA-
filtration units.
Final cleaning began with the wire-brushing of the ceiling-wall inter-
sections to remove any visible debris. The floor-wall intersections, in-
dented corners, crevices around doors, shelves, etc., were then cleaned with
a HEPA-filtered vacuum.
All of the vertical and horizontal surfaces were then wet-cleaned with
amended water. The contractor reportedly prepared the amended water solution
by mixing approximately 1 ounce each of 50 percent polyoxyethylene ester and
50 percent polyoxyethylene ether in 5 gallons of water.
The elevated surfaces were wiped first and then all other surfaces. All
the surfaces except the floors were wiped with sponges dampened with amended
water. A bucket of amended water was used by a single worker. The workers
did not appear to wipe the surfaces in any one direction. The sponges were
not replaced frequently, especially during the cleaning of elevated and
hard-to-access surfaces. Nor was the amended water changed frequently.
112
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After the walls, and other surfaces (shelves, ledges, etc.) were wet-
wiped, the floor was mopped with a clean mop head wetted with amended water.
No change in the water was observed during this procedure.
The last step in the final cleaning involved one complete mopping of
floors with a clean mop head and clean amended water. No aggressive cleaning
(i.e., air sweeping of all vertical and horizontal surfaces to dislodge any
remaining particulate) was conducted.
Wastewater from the wet-wiping and mopping operations was treated as
asbestos-containing water and placed in double-layered, 6-mil-thick, standard
disposal bags. These standard asbestos disposal bags which contained
wastewater were not placed in leak-tight containers or solidified with a
gelling compound. The sponges and mop heads used during cleaning were also
placed in these bags. The bags were not wet-wiped with amended water before
being removed from the abatement area.
Upon completing final cleaning, the abatement contractor requested a
final visual inspection by an onsite AST, who was the building owner's
representative. The AST conducted a visual inspection within 2 hours after
notification. The AST identified several areas that required further clean-
ing, baseboards, cornice ledges, and ceiling-wall intersections. After these
areas were recleaned, the AST conducted a final walk-through inspection to
assure that the identified areas were clean.
FINAL VISUAL INSPECTION BY NEW JERSEY DEPARTMENT OF HEALTH, ASBESTOS CONTROL
SERVICE
The site failed the first visual inspection because of the presence of
residual materials or granular loose debris on 1) corkboards on walls, 2)
tops of wood partitions under the stage, 3) light fixtures and electrical
cords, 4) ceiling-wall junctions, and 5) the carpeted area around the stage.
Five bulk samples were collected to characterize the makeup of the residual
debris. Samples were collected from the stage area, ceiling and walls, light
fixtures, and corkboards. Four of the five samples were found to contain
chrysotile asbestos. The samples were not sufficiently large to quantify the
percentage of asbestos in each.
The site failed the second visual inspection because of the presence of
debris 1) at wall-ceiling junctions, 2) above entry doorway, 3) on electrical
wires, and 4) on corkboards.
The site failed the third visual inspection because of the presence of
debris at wall-ceiling junctions and on the floor. Two bulk samples were
collected. The sample collected from the debris on the floor contained no
asbestos. The sample collected at the wall-ceiling junction contained 2
percent chrysotile.
The site passed the fourth visual inspection.
113
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AHERA CLEARANCE SAMPLING BY AST
The AHERA clearance sampling was initiated approximately 24 hours after
the site had passed the visual inspection. Using a hand-held electric leaf
blower, the AST conducted aggressive air sweeping of vertical and horizontal
surfaces for approximately 15 minutes, which is equivalent to approximately 5
minutes per 1700 square feet of floor area. No floor fans were used subse-
quently used to maintain air turbulence during sampling.
The clearance air samples were collected on 25-mm, 0.4-ym pore size,
polycarbonate membrane filters contained in a three-piece cassette with a
50-mm conductive cowl. The samples were collected at flow rates of approxi-
mately 10 liters per minute. The laboratory report indicates that the sam-
ples were analyzed in accordance with the AHERA mandatory TEM method.
Table 1-3 presents the results of the AST's clearance samples collected
inside the abatement area. The samples met the initial AHERA clearance
criterion, which stipulates an asbestos concentration of less than 70 struc-
tures per square millimeter (s/mm2). The average asbestos concentration for
the five inside samples was actually 36 s/mm2. The reason for the elevated
concentration (156 s/mm2) of one inside sample is not known.
TABLE 1-3. AHERA CLEARANCE SAMPLE RESULTS
Asbestos concentration
Sample Sample volume,
location liters s/mm2 s/cm3
Inside
Inside
Inside
Inside
Inside
2300
2231
2185
2400
2352
26
156
0
0
0
0.004
0.027
<0.005b
<0.005b
<0.005b
Outside samples and blanks were not analyzed because the aver-
age asbestos concentration for the five inside samples was less
than 70 s/mm2.
Sensitivity of the analytical method.
114
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CASE HISTORY J
SITE DESCRIPTION
This project abatement involved removal of approximately 5300 ft2 of
spray-applied asbestos-containing fireproofing from structural steel and
metal ceiling decks in a two-story school building. The abatement area
included two electrical transformer vaults and two mechanical equipment
rooms. The project specification indicated that the asbestos content of the
cementitious fireproofing was approximately 10 to 25 percent chrysotile.
VENTILATION AND NEGATIVE AIR PRESSURE
Six high-efficiency particulate air (HEPA) filtration units were oper-
ated during the final cleaning period, and five were operated during AHERA
clearance sampling. Table J-l presents the measured air-intake volume for
each unit. The average air-intake volume was 1358 ft3/min during final
cleaning and 1468 ft3/min during AHERA clearance sampling. Based on the
volume of the work area (78,435 ft3) and the combined average air-intake
volumes, the air exchange rates were approximately 6.3 air changes per hour
during final cleaning and 6.7 air changes per hour during AHERA clearance
sampling.
Figures J-l and J-2 compare the measured air-intake volume for each
HEPA-filtration unit operating during final cleaning and AHERA clearance
sampling, respectively, with the unit's nominal airflow. The actual
operating percentages of the nominal airflow ranged from 59 to 77 during
final cleaning and from 62 to 77 during AHERA clearance sampling.
Table J-2 presents the static pressure differential measured across the
containment barriers at one location. The number of locations tested was
determined by available access to the critical containment barriers. The
static pressure differential was -0.02 in. water during final cleaning and
-0.01 in. water during AHERA clearance sampling.
The asbestos safety technician (AST) did not monitor the static pressure
differential across the containment barrier. Instead ventilation smoke tubes
were used to check negative pressure visually (i.e., direction of airflow
through openings in the containment barrier, such as the decontamination
facility. Reportedly, these qualitative checks were performed each morning.
115
-------
TABLE J-l. AIRFLOW PERFORMANCE OF HEPA-FILTRATION UNITS
Airflow, ft /min
Model Unit Mean Min.
Max.
Std.
dev.
95% Confidence
interval
Lower Upper
Final cleaning
1
1
1
1
1
1
1
2
3
4
5
6
1176
1075
1299
1549
1512
1538
1008
941
1008
1344
1344
1344
1428
1260
1764
1848
1680
1680
123
85
196
157
103
93
1110
1030
1194
1465
1457
1489
1242
1121
1403
1632
1567
1588
AHERA clearance sampling
1
1
1
1
1
1
2
3
4
5
1239
1530
1528
1523
1523
1008
1260
1344
1344
1344
1512
1680
1680
1848
1680
153
130
108
148
126
1158
1460
1470
1444
1456
1320
1599
1585
1601
1589
TABLE J-2. STATIC PRESSURE DIFFERENTIALS
ACROSS CONTAINMENT BARRIERS
(in. water)
Test location
Final cleaning
-0.02
AHERA clearance
-0.01
116
-------
Percent of Nominal Airflow
100
80
60
40
20
59%
II
y~^^y
77%
59%
65%
/
76%
Hil
f^-^3
5
77%
34
HEPA Filtration Unit
(Same Model)
Figure J-1. Airflow performance for HEPA filtration systems
operating during final cleanup.
-------
Percent of Nominal Airflow
CO
100
80
60
40
20
62%
77%
76%
76%
76%
12345
HEPA Filtration Unit
(Same Model)
Figure J-2. Airflow performance for HEPA filtration systems
operating during AHERA clearance.
-------
The HEPA-filtration units were placed so that the makeup air entered the
work area through the personnel decontamination facility and waste load-out
port. The six operating units were positioned along exterior walls to faci-
litate venting of the exhaust through windows via an interconnected flexible
duct. The discharge air from the HEPA-filtration units was not monitored for
fiber content.
The contractor, who was responsible for maintaining the HEPA-filtration
units, stated that the prefilters and secondary filters were changed before
final cleaning was initiated; the HEPA filters were changed at the beginning
of the project. Thereafter, the prefilters and secondary filters were changed
when they became "visibly dirty." The HEPA filters were changed when an
audible alarm was actuated by a differential pressure sensor set by the
manufacturer.
FINAL CLEANING
Personal Protective Equipment
The personal protective equipment worn by the workers during final
cleaning consisted of full-body disposable coveralls and either full- or
half-facepiece air-purifying respirators equipped with dual-cartridge HEPA
filters.
Cleaning Procedures
Final cleaning began after the encapsulated plastic sheeting was removed
from the walls, floors, and other surfaces. The critical barriers, windows,
doors, stationary objects, and heating, ventilation, and air-conditioning
(HVAC) vents remained sealed. The HEPA filtration systems remained in ser-
vice.
Final cleaning was organized so the workers began in the areas farthest
from the personnel decontamination facility and worked toward it. No as-
sociation appeared to exist between the work direction and the location of
HEPA-filtration units.
Final cleaning began with the spraying of the abated substrate, walls,
plastic critical containment barriers, and other surfaces with water to
remove any loosely bound debris. The resultant asbestos-containing water on
the floor was gathered into pools by use of a rubber squeegee. The bulk of
the pooled water was scooped up with plastic bladed shovels, an approach that
worked surprisingly well. The water was put into double-layered, 6-mil-
thick, asbestos-disposal bags, which usually contained plastic that had been
removed from the walls and floors. The residual water removed with a wet
vacuum was also placed in these bags.
After the surfaces had dried, a vacuum equipped with a HEPA filter was
used to clean crevices around equipment brackets, doors, pipe hangers, floor-
wall interfaces, etc. The surfaces, especially the hard-to-clean areas such
as crevices around equipment brackets and hangers, were then swept with a
119
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hand-held, 1-horsepower leaf blower to dislodge any residual debris. The
abatement area was then vacated to allow the airborne debris to settle over-
night.
All of the vertical and horizontal surfaces were then wet-cleaned with
amended water. The contractor reportedly prepared the amended water solution
by mixing approximately 1 ounce each of 50 percent polyoxyethylene ester and
50 percent polyoxyethylene ether in 5 gallons of water.
The elevated horizontal and vertical surfaces were wiped first and then
all other surfaces. All the surfaces, except the floors were wiped with
cotton rags dampened with water. A bucket of water was either used by a
single worker or shared by several workers. The workers did not appear to
wipe the surfaces in any one direction. The cloth rags were not replaced
frequently, especially during the cleaning of elevated and hard-to-access
surfaces. Nor was the water changed frequently.
After the walls and other surfaces had been wet wiped, the floor was
mopped with a clean mop head wetted with amended water. No change in the
water was observed during this procedure.
The last step in the final cleaning effort involved removal of the
plastic sheeting covering the HEPA-filtration units and associated exhaust
ducts. The latter were covered with a plastic sleeve. According to the
contractor, this covering simplified the cleaning of this equipment.
Wastewater from the wet-wiping and mopping operations was treated as
asbestos-containing water and placed in double-layered 6-mil-thick standard
disposal bags. These standard asbestos disposal bags which contained
wastewater were not placed in leak-tight containers or solidified with a
gelling compound. The rags and mop heads used during cleaning also were
placed in these bags. The bags were not wet-wiped with amended water before
being removed from the abatement area.
Upon completing final cleaning, the abatement contractor requested a
final visual inspection by an onsite AST, who was the building owner's
representative. The AST conducted a visual inspection within 2 hours after
notification. The AST identified several areas, particularly elevated hori-
zontal surfaces, that required further cleaning. After these designated
areas were recleaned, the AST conducted a final walk-through inspection to
assure that the identified areas were clean.
FINAL VISUAL INSPECTION BY NEW JERSEY DEPARTMENT OF HEALTH, ASBESTOS CONTROL
SERVICE
The New Jersey Department of Health did not perform a final visual
inspection at this site.
120
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AHERA CLEARANCE SAMPLING
The AHERA clearance sampling was initiated approximately 18 hours after
the site had passed the visual inspection. Using a hand-held electric leaf
blower, the AST conducted aggressive air sweeping of vertical and horizontal
surfaces for approximately 20 minutes, which is equivalent to approximately 5
minutes per 1300 square feet of floor area. Four box-type floor fans with
18-inch blades were subsequently used to maintain air turbulence during
sampling.
The AST collected only two samples inside the work area for clearance
purposes. This practice is not in accordance with AHERA clearance proce-
dures, i.e., five samples must be collected inside the abatement area. These
samples were collected on 25-mm, 0.4-ym pore size, polycarbonate membrane
filters contained in a three-piece cassette with a 50-mm conductive cowl.
The samples were collected at flow rate of approximately 10 liters per
minute. Reportedly, the samples were analyzed by PCM in accordance with the
NIOSH 7400 Method.
Table J-3 presents the results of the AST's clearance samples collected
inside the abatement area.
TABLE J-3. CLEARANCE SAMPLE RESULTS BY PCM
Sample
location
Inside
Inside
Sample volume,
liters
1350
1350
Asbestos concentration,
f/cm3
<0.001a
0.002
a Sensitivity of the analytical method.
121
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CASE HISTORY K
SITE DESCRIPTION
This abatement project involved removal of approximately 8200 ft2 spray-
applied, asbestos-containing, acoustical plaster from an "egg crate" design
structural concrete ceiling in a single-story school building. The abatement
area included corridors, offices, and mechanical arts classrooms. The pro-
ject specification indicated that the asbestos content of the ceiling plaster
was approximately 10 to 25 percent chrysotile.
VENTILATION AND NEGATIVE AIR PRESSURE
Six high-efficiency particulate air (HEPA) filtration units were
operated during the final cleaning period, and four were operated during
AHERA clearance sampling. Table K-l presents the measured air-intake volume
for each unit. The average air-intake volume was 1566 ft3/min during final
cleaning and 1440 ft3/min during AHERA clearance sampling. Based on the
volume of the work area (115,000 ft3) and the combined average air-intake
volumes, the air-exchange rates were approximately 4.9 air changes per hour
during final cleaning and 3.0 air changes per hour during AHERA clearance
sampling.
Figures K-l and K-2 compare the measured air-intake volume of each
HEPA-filtration unit operating during final cleaning and AHERA clearance
sampling, respectively, with the unit's nominal airflow. The actual operat-
ing percentages of the nominal airflow ranged from 54 to 88 during final
cleaning and from 49 to 83 during AHERA clearance sampling.
Table K-2 presents the static pressure differential measured across the
containment barriers at one location. The number of locations tested was
determined by available access to the critical containment barriers. The
static pressure differential was -0.02 in. water during final cleaning and
-0.01 in. water during AHERA clearance sampling.
The asbestos safety technician (AST) did not monitor the static pressure
differential across the containment barriers. Instead ventilation smoke
tubes were used to check the negative pressure visually (i.e., direction of
air flow through openings in the containment barrier, such as the decon-
tamination facility). Reportedly, these qualitative checks were performed
each morning and afternoon.
122
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TABLE K-l. AIRFLOW PERFORMANCE OF HEPA-FILTRATION UNITS
Model
Airflow, ft /min
Unit Mean Min. Max.
Std.
dev.
95% Confidence
interval
Lower Upper
Final cleaning
1
2
2
2
2
2
1
2
3
4
5
6
1075
1769
1586
1649
1612
1706
924
1680
1344
1344
1512
1512
1260
1848
1848
1848
1680
1848
103
76
111
136
74
83
1020
1729
1527
1576
1572
1662
1130
1809
1644
1721
1651
1750
AHERA clearance sampling
1
2
2
2
1
2
3
4
975
1554
1570
1659
672
1176
1344
1428
1176
1848
1848
1848
128
181
159
134
907
1458
1485
1587
1044
1650
1655
1731
TABLE K-2. STATIC PRESSURE DIFFERENTIALS
ACROSS CONTAINMENT BARRIERS
(in. water)
Test location
Final cleaning
-0.02
AHERA clearance
-0.01
123
-------
Percent of Nominal Airflow
100
80
60 -
40
20-
88%
79%
82%
81%
85%
2345
HEPA Filtration Unit
Model 1
Model 2
Figure K-1. Airflow performance for HEPA filtration systems
operating during final cleanup.
-------
Percent of Nominal Airflow
ro
tn
100 -
2 3
HEPA Filtration Unit
Model 1
Model 2
Figure K-2. Airflow performance for HEPA filtration systems
operating during AHERA clearance.
-------
The HEPA-filtration units were placed so that the makeup air entered the
work area through the personnel decontamination facility and waste load-out
port. The five operating units were positioned along exterior walls to
facilitate venting of the exhaust through windows via an interconnected
flexible duct. The discharge air from the HEPA-filtration units was not
monitored for fiber content.
The contractor, who was responsible for maintaining the HEPA-filtration
units, stated that the prefilters and secondary filters were changed before
final cleaning was initiated and the HEPA filters were changed at the
beginning of the project. Thereafter, the prefilters and secondary filters
were changed when they became "visibly dirty." The HEPA filters were changed
when an audible alarm was actuated by a differential pressure sensor set by
the manufacturer.
FINAL CLEANING
Personal Protective Equipment
The personal protective equipment worn by the workers during final
cleaning consisted of full-body disposable coveralls and either full- or
half-facepiece air-purifying respirators equipped with dual-cartridge HEPA
filters.
Cleaning Procedures
Final cleaning began after the encapsulated plastic sheeting was removed
from the walls, floors, and other surfaces. The critical barriers, windows,
doors, lighting fixtures, stationary objects, and heating, ventilation, and
air-conditioning (HVAC) vents remained sealed. The HEPA filtration units
remained in service.
Final cleaning was organized so the workers began in the areas farthest
from the personnel decontamination facility and worked toward it. No as-
sociation appeared to exist between the work direction and the location of
HEPA-filtration units.
Final cleaning began with cleaning of surfaces with a vacuum equipped
with a HEPA filter. Particular attention was given to vacuuming the joints
between planks of the hardwood floor, floor-wall intersections, and crevices
around doors.
All of the vertical and horizontal surfaces were then wet-cleaned with
amended water. The contractor reportedly prepared the amended water solution
by mixing approximately 1 ounce each of 50 percent polyoxyethylene ester and
50 percent polyoxyethylene ether in 5 gallons of water.
The elevated horizontal (light fixtures) and vertical surfaces were
wiped first, and then all the other surfaces. All the surfaces except the
floors were wiped with cotton rags dampened with amended water. A bucket of
126
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amended water was either used by a single worker or shared by several work-
ers. The workers did not appear to wipe the surfaces in any one direction.
The cloth rags were not replaced frequently, especially during the cleaning
of elevated and hard-to-access surfaces. Nor was the amended water changed
frequently.
After the walls and other surfaces were wet-wiped, the floor was hand-
wiped with clean cotton rags wetted with amended water. No changes in the
water were observed during this procedure.
No aggressive cleaning (i.e., air sweeping of all vertical and hori-
zontal surfaces to dislodge any remaining particulate) was conducted.
Wastewater from the wet-wiping and mopping operations was treated as
asbestos-containing water and placed in double-layered 6-mil-thick, standard
disposal bags. These standard asbestos disposal bags which contained
wastewater were not placed in leak-tight containers or solidified with a
gelling compound. The rags and mop heads used during cleaning also were
placed in these bags. The bags were not wet-wiped with amended water before
being removed from the abatement area.
Upon completing final cleaning, the abatement contractor requested a
final visual inspection by an onsite AST, the building owner's representa-
tive. The AST conducted a visual inspection within 2 hours after notifica-
tion. The AST identified several areas that required further cleaning,
including indented corners, door frames, light fixtures, electrical conduit,
and crevices along baseboards. After these designated areas were recleaned,
the AST conducted a final walk-through inspection to assure that the identi-
fied areas were clean.
FINAL VISUAL INSPECTION BY NEW JERSEY DEPARTMENT OF HEALTH, ASBESTOS CONTROL
SERVICE
The site failed the first visual inspection because of the presence of
gross debris on the concrete substrate surfaces, under pipe hangers, on
vertical and horizontal surfaces, and on the scaffolding equipment. Seven
bulk samples were collected to characterize the residual debris found on the
floor, at ceiling-wall intersections, and on the top of a wooden beam, a
window, and a pipe. Asbestos was identified in four of the seven samples;
however, the samples were not sufficiently large to quantify the percentage
of asbestos in each.
The site failed the second visual inspection because of gross debris
found behind immovable wooden shelves, at floor-wall junctions, behind
student lockers, on horizontal surfaces, and on other immovable objects.
Four bulk samples were collected to characterize the residual debris found on
the horizontal surfaces (shelves) and floors. Asbestos was identified in two
of the four bulk samples; however, the' samples were not sufficiently large to
quantify the percentage of asbestos in each.
127
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The site failed the third visual inspection because of gross debris
found on horizontal surfaces, behind immovable objects, and at floor-wall
intersections. Conditions were found to be much the same as during earlier
visual inspections.
The site passed the fourth visual inspection.
AHERA CLEARANCE SAMPLING BY AST
The AHERA clearance sampling was initiated approximately 24 hours after
the site had passed the visual inspection. Using a hand-held electric leaf
blower, the AST conducted aggressive air sweeping of vertical and horizontal
surfaces for approximately 20 minutes, which is equivalent to approximately 5
minutes per 2100 square feet of floor area. Four pedestal-type floor fans
with 24-inch blades were used subsequently to maintain air turbulence during
sampling.
The clearance air samples were collected on 25-mm, 0.8-pm pore size,
mixed cellulose ester membrane filters contained in a three-piece cassette
with a 50-mm conductive cowl. The samples were collected at flow rates of
approximately 10 liters per minute. The laboratory report, indicates the
samples were analyzed in accordance with the AHERA mandatory TEM method.
Table K-3 presents the results of the clearance samples the AST col-
lected inside the abatement area. The samples met the initial AHERA clear-
ance criterion by having an average asbestos concentration of less than 70
structures per square millimeter (s/mm2). The average asbestos concentration
for the five inside samples was actually 0 s/mm2.
TABLE K-3. AHERA CLEARANCE SAMPLE RESULTS
Asbestos concentration
Sample
location
Inside
Inside
Inside
Inside
Inside
Sample volume,
liters
Not Reported
Not Reported
Not Reported
Not Reported
Not Reported
s/mm2
0
0
0
0
0
s/cm3
<0.005b
<0.005b
<0.005b
<0.005b
<0.005b
Outside samples and blanks were not analyzed because the average
asbestos concentration for the five inside samples was less than
70 s/mm2.
Sensitivity of the analytical method.
128
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CASE HISTORY L
SITE DESCRIPTION
This abatement project involved removal of approximately 1600 ft2 of
trowel-applied, asbestos-containing, acoustical ceiling plaster from a
single-story school building. The abatement area was an auditorium. The
project specification indicated that the asbestos content of the ceiling
plaster was approximately 15 to 25 percent chrysotile.
VENTILATION AND NEGATIVE-AIR PRESSURE
Three high-efficiency particulate air (HEPA) filtration units were
operated during the final cleaning period, and three were operated during
AHERA clearance sampling. Table L-l presents the measured air-intake volume
for each unit. The average air-intake volume was 1260 ft3/min during final
cleaning and 1305 ft3/min during AHERA clearance sampling. Based on the
volume of the work area (36,000 ft3) and the combined average air-intake
volumes, the air exchange rates were approximately 6.3 air changes per hour
during final cleaning and 6.5 air changes per hour during AHERA clearance
sampling.
TABLE L-l. AIRFLOW PERFORMANCE OF HEPA-FILTRATION UNITS
Airflow, ft /min
Model Unit Mean Min. Max.
Std.
dev.
95% Confidence
interval
Lower Upper
Final Cleaning
1
2
3
1
2
3
1586
657
1538
1344
530
1176
1848
734
1848
194
67
165
1482
621
1451
1689
693
1626
AHERA clearance sampling
1
2
3
1
2
3
1533
665
1717
1176
571
1512
1848
734
1848
194
61
94
1430
632
1667
1636
697
1767
129
-------
Figures L-l and 1-2 compare the measured air-intake volume of each
HEPA-fiHration unit operating during final cleaning and AHERA clearance
sampling, respectively, with the unit's nominal airflow. The actual operat-
ing percentages of the nominal airflow ranged from 66 to 79 during final
cleaning and from 67 to 86 during AHERA clearance sampling.
Table L-2 presents the static pressure differential measured across the
containment barriers at three locations. The number of locations tested was
determined by available access to the critical containment barriers. The
static pressure differential was -0.01 in. water during both final cleaning
and AHERA clearance sampling.
TABLE L-2. STATIC PRESSURE DIFFERENTIALS
ACROSS CONTAINMENT BARRIERS
(in. water)
Test location Final cleaning AHERA clearance
1
2
3
-0.01
-0.01
-0.01
-0.01
-0.01
-0.01
The asbestos safety technician (AST) did not monitor the static pressure
differential across the containment barriers. Instead, ventilation smoke
tubes were used to check the pressure visually (i.e., direction of air flow
through openings in the containment barrier, such as the decontamination
facility). Reportedly, these qualitative checks were performed each morning.
The HEPA-filtration units were placed so that the makeup air entered the
work area through the personnel decontamination facility and waste load-out
port. The three operating units were vented through a doorway via an inter-
connected flexible ducts that passed through a hallway outside of the abate-
ment area. This is particularly noteworthy, because the flexible duct from
two of the three units was torn and a percentage of the exhaust air was
released into the building. The discharge air from the HEPA-filtration units
was not monitored for fiber content.
The contractor, who was responsible for maintaining the HEPA-filtration
units, stated that the prefliters and secondary filters were changed before
final cleaning was initiated, and the HEPA filters were changed at the begin-
ning of the project. Thereafter, the prefiHers were changed when they
became "visibly dirty, and the secondary filters were changed daily. The
HEPA filters were changed when an audible alarm was actuated by a differen-
tial pressure sensor set by the manufacturer.
130
-------
Percent of Nominal Airflow
100 -i
80 -
60 -
40
20 -
79%
1
66%
HEPA Filtration Unit
Model 1
Model 2
77%
~7
Model 3
Figure L-1. Airflow performance for HEPA filtration systems
operating during final cleanup.
-------
00
IV)
Percent of Nominal Airflow
100
80 J
60 -
40
20 -
77%
67%
HEPA Filtration Unit
Model 1
Model 2
86%
Model 3
\
Figure L-2. Airflow performance for HEPA filtration systems
operating during AHERA clearance.
-------
FINAL CLEANING
Personal Protective Equipment
The personal protective equipment worn by the workers during final
cleaning consisted of full-body disposable coveralls and either full- or
half-facepiece air-purifying respirators equipped with dual-cartridge HEPA
filters.
Cleaning Procedures
Final cleaning began after the plastic sheeting was removed from the
walls, floors, and all auditorium chairs. The critical barriers, doors, and
heating, ventilation, and air-conditioning (HVAC) vents remained sealed. The
HEPA filtration units remained in service.
Final cleaning was organized so the workers began in the areas farthest
from the personnel decontamination facility and worked toward it. No asso-
ciation appeared to exist between work direction and the location of HEPA-
filtration units.
Final cleaning began with the wire-brushing of the ceiling-wall inter-
sections. The surfaces were then cleaned with a HEPA- filtered vacuum.
Particular attention was given to vacuuming the crevices around the floor-
mounting brackets of the auditorium chairs.
All of the vertical and horizontal surfaces were then wet-cleaned with
amended water. The contractor reportedly prepared the amended water solution
by mixing approximately 1 ounce each of 50 percent polyoxyethylene ester and
50 percent polyoxyethylene ether in 5 gallons of water.
The elevated vertical surfaces were wiped first and then all other
surfaces. All the surfaces except the floors were wiped with absorbent paper
towels dampened with amended water. A bucket of amended water was either
used by a single worker or shared by several workers. The workers did not
appear to wipe the surfaces in any one direction. The paper towels were not
replaced frequently, especially during the cleaning of elevated surfaces.
Nor was the amended water changed frequently.
After the walls and plastic-covered auditorium chairs were wet-wiped,
the floor was mopped with a clean mop head wetted with amended water. No
changes in the water were observed during this procedure.
Final cleaning involved one complete mopping of the floor with a clean
mop head and amended water. No aggressive cleaning (i.e., air sweeping of
all vertical and horizontal surfaces to dislodge any remaining particulate)
was conducted.
Wastewater from the wet-wiping and mopping operations was treated as
asbestos-containing water and placed in double-layered, 6-mil-thick, standard
disposal bags. A commercial gelling compound was added to the bag to
133
-------
solidify the wastewater. These standard asbestos disposal bags which
contained wastewater were not placed in leak-tight containers. The paper
towels and mop heads used during cleaning also were placed in these bags.
The bags were not wet-wiped with amended water before being removed from the
abatement area.
Upon completing final cleaning, the abatement contractor requested a
final visual inspection by an onsite AST, who was the building owner's
representative. The AST conducted a visual inspection within 2 hours after
notification. The AST identified several areas, particularly elevated hori-
zontal surfaces, that required further cleaning. After these designated
areas were recleaned, the AST conducted a final walk-through inspection to
assure that the identified areas were clean.
FINAL VISUAL INSPECTION BY NEW JERSEY DEPARTMENT OF HEALTH, ASBESTOS CONTROL
SERVICE
The site failed the first visual inspection because of the presence of
debris on the upper ledge of the auditorium ceiling and on the wooden blocks
used to hold up the polyethylene walls. One bulk sample was collected to
characterize the debris found on the ceiling ledge. Chrysotile asbestos was
identified in this sample, but the sample was not sufficiently large enough
to quantify the asbestos content.
The site passed the second visual inspection.
AHERA CLEARANCE SAMPLING BY AST
The AHERA clearance sampling was initiated approximately 24 hours after
the site had passed the visual inspection. Using a hand-held electric leaf
blower, the AST conducted aggressive air sweeping of vertical and horizontal
surfaces for approximately 10 minutes, which is equivalent to approximately 5
minutes per 800 ft2 of floor area. Two box-type floor fans with 18-inch
blades were subsequently used to maintain air turbulence during sampling.
The clearance air samples were collected on 25-mm, 0.45-ym pore size,
mixed cellulose ester membrane filters contained in a three-piece cassette
with a 50-mm conductive cowl. The samples were collected at flow rates of
approximately 10 liters per minute. The laboratory report indicates that the
samples were analyzed in accordance with the AHERA mandatory TEM method.
Table L-3 presents the results of the clearance samples the AST col-
lected inside the abatement area. The samples met the initial AHERA clear-
ance criterion, i.e., an average asbestos concentration of less than 70
structures per square millimeter (s/mm2). The average asbestos concentration
for the five inside samples was actually 48 s/mm2. The reason for the
elevated concentration (139 s/mm2) for one of the inside samples is not known.
134
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TABLE
Sample
location
Inside
Inside
Inside
Inside
Inside
L-3. AHERA CLEARANCE
SAMPLE RESULTS
Asbestos concentration
liters
1440
1320
1440
1440
1440
s/mm2 s/cm3
139 0.037
31 0.009
17 0.005
16 0.005
35 0.009
a Outside samples and blanks were not analyzed because
the average asbestos concentration for the five in-
side samples was less than 70 s/mm2.
Sensitivity of the analytical method.
135
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CASE HISTORY M
SITE DESCRIPTION
This abatement project involved removal of asbestos-containing thermal
insulation materials (preformed block and air-cell-paper pipe insulation)
from a three-story school building. The abatement area included corridors,
classrooms, offices, storage areas, and a gymnasium. The project specifi-
cation indicated that the asbestos content of the thermal insulation was
approximately 40 to 60 percent chrysotile. The specifications did not quan-
tify the amount of asbestos-containing material in each location.
VENTILATION AND NEGATIVE AIR PRESSURE
Three high-efficiency particulate air (HEPA) filtration units were
operated during the final cleaning period, and three were operated during
AHERA clearance sampling. Table M-l presents the measured air-intake volume
for each unit. The average air-intake volume was 1630 ft3/min during final
cleaning and 1501 ft3/min during AHERA clearance sampling. Based on the
volume of the work area (33,300 ft3) and the combined average air-intake
volumes, the air exchange rates were approximately 8.8 air changes per hour
during final cleaning and 8.1 air changes per hour during AHERA clearance
sampling.
TABLE M-l. AIRFLOW PERFORMANCE OF HEPA-FILTRATION UNITS
Airflow, ft /min
Model Unit Mean Min.
Max.
Std.
dev.
952 Confidence
interval
Lower Upper
Final cleaning
1
2
2
1
2
3
1549
1633
1709
1176
1344
1478
1680
1848
1932
122
168
118
1484
1543
1646
1614
1722
1772
AHERA clearance sampling
1
2
2
1
2
3
1170
1664
1670
1008
1344
1512
1344
1848
1848
117
149
102
1107
1585
1615
1232
1744
1724
136
-------
Figures M-l and M-2 compare the measured air-intake volume for each
HEPA-filtration unit operating during final cleaning and AHERA clearance
sampling, respectively, with the unit's nominal airflow. The actual operat-
ing percentages of the nominal airflow ranged from 77 to 85 during final
cleaning and from 59 to 84 during AHERA clearance sampling.
Table M-2 presents the static pressure differential measured across the
containment barriers at two locations. The number of locations tested was
determined by available access to the critical containment barriers. The
static pressure differential was -0.02 in. water during final cleaning and
ranged from -0.01 to -0.02 in. water during AHERA clearance sampling.
TABLE M-2. STATIC PRESSURE DIFFERENTIALS
ACROSS CONTAINMENT BARRIERS
(in. water)
Test location Final cleaning AHERA clearance
1
2
-0.02
-0.02
-0.02
-0.01
The asbestos safety technician (AST) did not monitor the static pressure
differential across the containment barriers. Instead ventilation smoke
tubes were used to check negative pressure visually (i.e., direction of air
flow through openings in the containment barrier, such as the decontamination
facility and waste load-out port). Reportedly, these qualitative checks were
performed each morning and afternoon.
The HEPA-filtration units were placed so that the makeup air entered the
work area through the personnel decontamination facility and waste load-out
port. The three operating units were positioned along exterior walls to
facilitate venting the exhaust through windows via an interconnected flexible
duct. The discharge air from the HEPA-filtration units was not monitored for
fiber content.
The contractor, who was responsible for maintaining the HEPA-filtration
units, stated that the prefilters and secondary filters were changed before
final cleaning was initiated and the HEPA filter was changed at the beginning
of the project. Thereafter, the prefilters were changed daily, and the
secondary filters were changed when they became "visibly dirty." The HEPA
filters were changed every 600 to 700 hours (as recommended by the manu-
facturer) or when an audible alarm was actuated by a differential pressure
sensor set by the manufacturer.
FINAL CLEANING
Personal Protective Equipment
The personal protective equipment worn by the workers during final
cleaning consisted of full-body disposable coveralls and either full- or
137
-------
Percent of Nominal Airflow
GJ
CO
100
80-
60 -
40
20 -
77%
82%
85%
HEPA Filtration Unit
Model 1
Model 2
Figure M-1. Airflow performance for HEPA filtration systems
operating during final cleanup.
-------
Percent of Nominal Airflow
GO
100
80 -
60 -
40
20
59%
83%
HEPA Filtration Unit
Model 1
Model 2
Figure M-2. Airflow performance for HEPA filtration systems
operating during AHERA clearance.
-------
half-facepiece air-purifying respirators equipped with dual cartridge HEPA
filters.
Cleaning Procedures
Final cleaning began after the encapsulated plastic sheeting was removed
from the walls, floors, and other surfaces. The critical barriers, doors,
stationary objects, and heating, ventilation, and air-conditioning (HVAC)
vents remained sealed. The HEPA filtration units remained in service.
Final cleaning was organized so the workers began in the areas farthest
from the personnel decontamination facility and worked toward it. No as-
sociation appeared to exist between work direction and the location of the,_
HEPA-filtration units.
Final cleaning began with the brushing of the pipes to remove any
visible debris. These surfaces and points where the pipes penetrated walls
were cleaned with a HEPA-filtered vacuum. Detailed cleaning of the joints
between the planks of the hardwood floor in the gymnasium and the floor-wall
intersection was also accomplished with a HEPA-filtered vacuum.
All of the vertical and horizontal surfaces were then wet-cleaned with
amended water. The contractor reportedly prepared the amended water solution
by mixing approximately 1 ounce each of 50 percent polyoxyethylene ester and
50 percent polyoxyethylene ether in 5 gallons of water.
The elevated horizontal and vertical surfaces were wiped first and then
all other surfaces. All the surfaces except the floors were wiped with
absorbent paper towels dampened with amended water. A bucket of amended
water was either used by a single worker or shared by several workers. The
workers did not appear to wipe the surfaces in any one direction. The paper
towels were not replaced frequently, especially during the cleaning of ele-
vated and hard-to-access surfaces. Nor was the amended water changed fre-
quently.
After the walls and other surfaces were wet-wiped, the floor was mopped
with a clean mop head wetted with amended water. No changes in the water
were observed during this procedure.
The last step in the final cleaning was a complete wet-mopping of the
floors with a clean mop head and amended water. No aggressive cleaning
(i.e., air sweeping of all vertical and horizontal surfaces to dislodge any
remaining particulate) was conducted.
Wastewater from the wet-wiping and mopping operations was treated as
asbestos-containing water and placed in double-layered, 6-mil-thick, standard
disposal bags. These standard asbestos disposal bags which contained
wastewater were not placed in leak-tight containers or solidified with a
gelling compound. The rags and mop heads used during cleaning also were
placed in these bags. The bags were not wet-wiped with amended water before
being removed from the abatement area.
140
-------
Upon completing final cleaning, the abatement contractor requested a
final visual inspection by an onsite AST, who was the building owner's
representative. The AST conducted a visual inspection within 2 hours after
notification. The AST identified several areas that required further clean-
ing, including debris on elbows and joints of pipes, and debris at wall
penetrations of pipes. After these designated areas were recleaned, the AST
conducted a final walk-through inspection to assure that the identified areas were
free of debris.
FINAL VISUAL INSPECTION BY NEW JERSEY DEPARTMENT OF HEALTH, ASBESTOS CONTROL
SERVICE
The site failed the first visual inspection because of the presence of
debris on the floors (in corners and behind pipes at the walls) and on pipe
joints and elbows. Four bulk samples were collected to characterize the
residual debris found on the floors and pipes. The asbestos content of the
debris found on the floor was approximately 30 percent chrysotile. Chryso-
tile asbestos was also identified in the residual debris found on the pipes;
however, the samples were not large enough to quantify the asbestos content.
The site failed the second visual inspection because of debris on pipes,
on the floors, and in wall penetrations. One bulk sample was collected to
characterize the debris found on the pipes. Although chrysotile asbestos was
identified in the residual debris found on the pipes, the sample was not
large enough to quantify the asbestos content.
The site passed the third visual inspection.
AHERA CLEARANCE SAMPLING BY AST
The AHERA clearance sampling was initiated approximately 24 hours after
the site had passed the visual inspection. Using a hand-held electric leaf
blower, the AST conducted aggressive air sweeping of vertical and horizontal
surfaces for approximately 60 minutes, which is equivalent to approximately 5
minutes per 260 ft2 of floor area. Floor fans were not used subsequently to
maintain air turbulence during sampling.
The clearance air samples were collected on 25-mm, 0.45-pm pore size,
mixed cellulose ester membrane filters contained in a three-piece cassette
with a 50-mm conductive cowl. The samples were collected at flow rates of
approximately 9.25 liters per minute. The laboratory report indicates, the
samples were analyzed in accordance with the AHERA mandatory TEN method.
Table M-3 presents the results of the clearance samples the AST col-
lected inside the abatement area. The samples met the initial AHERA clear-
ance criterion, i.e., an average asbestos concentration of less than 70
structures per square millimeter (s/mm2). The average asbestos concentration
for the five inside samples was actually 10 s/mm2.
141
-------
TABLE M-3. AHERA CLEARANCE SAMPLE RESULTS
Sample
location
Inside
Inside
Inside
Inside
Inside
Sample volume,
liters
2035
2035
2035
2035
2035
Asbestos
s/mm2
0
0
0
0
50
concentration
s/cm3
<0.005b
<0.005b
<0.005b
<0.005b
Not Reported
a Outside samples and blanks were not analyzed because the aver-
age asbestos concentration for the five inside samples was
less than 70 s/mm2.
Sensitivity of the analytical method.
142
-------
CASE HISTORY N
SITE DESCRIPTION
This abatement project involved removal of approximately 11,000 ft2 of
spray-applied, asbestos-containing, acoustical plaster from an "egg crate"
design structural concrete ceiling in a single-story school building. The
abatement area included corridors, classrooms, offices, and mechanical arts
classrooms. The project specification indicated that the asbestos content of
the ceiling plaster was approximately 10 to 25 percent chrysotile.
VENTILATION AND NEGATIVE AIR PRESSURE
Four high-efficiency particulate air (HEPA) filtration units were oper-
ated during the final cleaning period, and four were operated during AHERA
clearance sampling. Table N-l presents the measured air-intake volume for
each unit. The average air-intake volume was 1245 ft3/min during final
cleaning and 1253 ft3/min during AHERA clearance sampling. Based on the
volume of the work area (66,300 ft3) and the combined average air-intake
volumes, the air exchange rates were approximately 4.5 air changes per hour
during final cleaning and 4.6 air changes per hour during AHERA clearance
sampling.
TABLE N-l. AIRFLOW PERFORMANCE OF HEPA-FILTRATION UNITS
Model
1
1
1
1
Unit
1
2
3
4
Airflow, ft /min
Mean
672
1007
1691
1609
Min.
Final
528
792
1320
1320
Max.
cleaning
766
1188
1848
1848
Std.
dev.
112
118
142
145
95% Confidence
interval
Lower
612
944
1616
1531
Upper
731
1069
1767
1686
AHERA clearance sampling
1
1
1
1
1
2
3
4
586
1246
1596
1584
502
1056
1452
1320
660
1452
1716
1848
52
123
100
140
558
1180
1543
1509
614
1311
1649
1659
143
-------
Figures N-l and N-2 compare the measured air-intake volume for each
HEPA-filtration unit operating during final cleaning and AHERA clearance
sampling, respectively, with the unit's nominal airflow. The actual operat-
ing percentages of the nominal airflow ranged from 34 to 85 during final
cleaning and from 29 to 80 during AHERA clearance sampling.
Table N-2 presents the static pressure differential measured across the
containment barriers at one location. The number of locations tested was
determined by available access to the critical containment barriers. The
static pressure differential was -0.01 in. water during both final cleaning
and AHERA clearance sampling.
TABLE N-2. STATIC PRESSURE DIFFERENTIALS
ACROSS CONTAINMENT BARRIERS
(in. water)
Test location Final cleaning AHERA clearance
1 -0.01 -0.01
The asbestos safety technician (AST) did not monitor the static pressure
differential across the containment barriers. Instead ventilation smoke
tubes were used to check the negative pressure visually (i.e., direction of
airflow through openings in the containment barrier, such as the decontami-
nation facility and waste load-out port). Reportedly, these qualitative
checks were performed each morning.
The HEPA-filtration units were placed so that the makeup air entered the
work area through the personnel decontamination facility. Three of the four
operating units were positioned along exterior walls to facilitate venting
the exhaust through windows via an interconnected flexible duct. The exhaust
of the fifth unit was vented through a doorway via an interconnected flexible
duct that passed through a room outside of the abatement area. The discharge
air from the HEPA-filtration units was not monitored for fiber content.
The contractor, who was responsible for maintaining the HEPA-filtration
units, stated that the prefilters and secondary filters were changed before
final cleaning was initiated and the HEPA filter was changed at the begin-
ning of the project. Thereafter, the prefilters and secondary filters were
changed when they became "visibly dirty." The HEPA filters were changed when
an audible alarm was actuated by a differential pressure sensor set by the
manufacturer.
FINAL CLEANING
Personal Protective Equipment
The personal protective equipment worn by the workers during final
cleaning consisted of full-body disposable coveralls and either full- or
144
-------
Percent of Nominal Airflow
en
100
80
60
40
20
34%
85%
mi
50%
80%
1234
HEPA Filtration Unit
(Same Model)
Figure N-1. Airflow performance for HEPA filtration systems
operating during final cleanup.
-------
Percent of Nominal Airflow
100
80
60
40
20
29%
80%
62%
79%
/
1234
HEPA Filtration Unit
(Same Model)
Figure N-2. Airflow performance for HEPA filtration systems
operating during AHERA clearance.
-------
half-facepiece air-purifying respirators equipped with dual-cartridge HEPA
filters.
Cleaning Procedures
Final cleaning began after the encapsulated plastic sheeting was removed
from the walls and floors. The critical barriers, doors, lighting fixtures,
stationary objects such as machinery, and heating, ventilation, and air-
conditioning (HVAC) vents remained sealed. The HEPA filtration units re-
mained in service.
The final cleaning was organized so the workers began in the areas
farthest from the personnel decontamination facility and worked toward it.
No association appeared to exist between the work direction and the location
of HEPA-filtration units.
Final cleaning began with the wire-brushing of the concrete substrate
surface to remove any visible debris. The ceiling, walls, plastic critical
containment barriers, and other surfaces were then sprayed with water to
remove any loosely bound debris. The resultant asbestos-containing water on
the floor was gathered into pools by use of a rubber squeegee. The bulk of
the pooled water was scooped up with plastic bladed shovels. The water was
containerized in double-layered, 6-mil-thick, asbestos-disposal bags, which
usually contained plastic that had been removed from the walls and floors.
The residual water removed with a HEPA-filtered wet vacuum was also placed in
the disposal bags.
After the surfaces had dried, a vacuum equipped with a HEPA filter was
used to clean crevices around windows, doors, room partitions, shelves,
floor-wall interfaces, etc.
All of the vertical and horizontal surfaces were then wet-cleaned with
amended water. The contractor reportedly prepared the amended water solution
by mixing approximately 1 ounce each of 50 percent polyoxyethylene ester and
50 percent polyoxyethylene ether in 5 gallons of water.
The elevated horizontal and vertical surfaces were wiped first and then
all the other surfaces. All the surfaces except the floors were wiped with
cotton rags dampened with amended water. A bucket of amended water was
either used by a single worker or shared by several workers. The workers did
not appear to wipe the surfaces in any one direction. The cloth rags were
not replaced frequently, especially during the cleaning of elevated and
hard-to-access surfaces. Nor was the amended water changed frequently.
After the walls, windows, and other surfaces (shelves, ledges, plastic-
covered stationary equipment, etc.) were wet-wiped, the floor was mopped with
a clean mop head wetted with amended water. No changes in the water were
observed during this procedure.
147
-------
The last step in the final cleaning involved one complete wet-mopping of
the floors with clean mop heads and amended water. No aggressive cleaning
(i.e., air sweeping of all vertical and horizontal surfaces to dislodge any
remaining particulate) was conducted.
Wastewater from the wet-wiping and mopping operations was treated as
asbestos-containing water and placed in double-layered, 6-mil-thick, standard
disposal bags. These standard asbestos disposal bags which contained
wastewater were not placed in leak-tight containers or solidified with a
gelling compound. The rags and mop heads used during cleaning were also
placed in these bags. The bags were not wet-wiped with amended water before
being removed from the abatement area.
Upon completing final cleaning, the abatement contractor requested a
final visual inspection by an onsite AST, who was the building owner's
representative. The AST conducted a visual inspection within 2 hours after
notification. The AST identified several areas that required further clean-
ing, including corners at floor-wall intersections and the tops of lighting
fixtures. After these designated areas were recleaned, the AST conducted a
final walk-through inspection to assure that the identified areas were clean.
FINAL VISUAL INSPECTION BY NEW JERSEY DEPARTMENT OF HEALTH, ASBESTOS CONTROL
SERVICE
The site failed the first visual inspection because of the presence of
debris on light fixtures, the tops of heating elements, on conduit pipe, on
the walls behind ventilation ducts, and on the floors. One bulk sample was
taken to characterize the residual debris found on the walls. Chrysotile
asbestos was identified in this sample; however, the sample was not large
enough to quantify the asbestos content.
The site passed the second visual inspection.
AHERA CLEARANCE SAMPLING BY AST
The AHERA clearance sampling was initiated approximately 24 hours after
the site passed the visual inspection. Using a hand-held electric leaf
blower, the AST conducted aggressive air sweeping of vertical and horizontal
surfaces for approximately 13 minutes, which is equivalent to approximately 5
minutes per 4,200 ft2 of floor area. Two pedestal-type floor fans with
18-inch blades were subsequently used to maintain air turbulence during
sampling.
The clearance air samples were collected on 25-mm, 0.45-ym pore size,
mixed cellulose ester membrane filters contained in a three-piece cassette
with a 50-mm conductive cowl. The samples were collected at flow rates of
approximately 9.5 liters per minute. The laboratory report indicates that
the samples were analyzed in accordance with the AHERA mandatory TEM method.
143
-------
Table N-3 presents the results of the clearance samples the AST col-
lected inside the abatement area. The samples met the initial AHERA clear-
ance criterion, i.e., an average asbestos concentration of less than 70
structures per square millimeter (s/mmz). The average asbestos concentration
for the five inside samples was actually 0 s/mm2.
TABLE N-3. AHERA CLEARANCE SAMPLE RESULTS
Sample
location
Inside
Inside
Inside
Inside
Inside
Sample volume,
liters
Not reported
Not reported
Not reported
Not reported
Not reported
Asbestos concentration
s/mm2 s/cm3
0 <0.005b
0 <0.005b
0 <0.005b
0 <0.005b
0 <0.005b
Outside samples and blanks were not analyzed because the aver-
age asbestos concentration for the five inside samples was
less than 70 s/mm2.
Sensitivity of the analytical method.
149
-------
CASE HISTORY 0
SITE DESCRIPTION
This abatement project involved removal of approximately 2,100 ft2 of
2-ft by 4-ft lay-in, asbestos-containing, acoustical ceiling tiles from a
two-story school building. The abatement area included corridors, class-
rooms, and offices. The project specification indicated that the asbestos
content of the ceiling plaster was approximately 5 to 10 percent amosite.
VENTILATION AND NEGATIVE-AIR PRESSURE
Three high-efficiency particulate air (HEPA) filtration units were
operated during the final cleaning period, and three were operated during
AHERA clearance sampling. Table 0-1 presents the measured air-intake volume
for each unit. The average air-intake volume was 1621 ft3/min during final
cleaning and 1453 ft3/min during AHERA clearance sampling. Based on the
volume of the work area (44,400 ft3) and the combined average air-intake
volumes, the air exchange rates were approximately 6.6 air changes per hour
during final cleaning and 5.9 air changes per hour during AHERA clearance
sampling.
TABLE 0-1. AIRFLOW PERFORMANCE OF HEPA-FILTRATION UNITS
Airflow, ft /min
Model
Unit Mean
Min.
Max.
Std.
dev.
95% Confidence
interval
Lower Upper
Final cleaning
1
1
1
1
2
3
1549
1680
1633
1344
1428
1512
1764
1848
1848
133
115
107
1478
1619
1576
1619
1741
1690
AHERA clearance sampling
1
1
1
1
2
3
1412
1402
1596
1176
1008
1344
1680
1680
1680
161
180
126
1327
1306
1477
1498
1498
1610
150
-------
Figures 0-1 and 0-2 compare the measured air-intake volume for each
HEPA-filtration unit operating during final cleaning and AHERA clearance
sampling, respectively, with the unit's nominal airflow. The actual operat-
ing percentage of the nominal air flow ranged from 77 to 84 percent during
final cleaning and from 70 to 77 percent during AHERA clearance sampling.
Table 0-2 presents the static pressure differential measured across the
containment barriers at two locations. The number of locations tested was
determined by available access to the critical containment barriers. The
static pressure differential was -0.02 in. water during both final cleaning
AHERA clearance sampling.
TABLE 0-2. STATIC PRESSURE DIFFERENTIALS
ACROSS CONTAINMENT BARRIERS
(in. water)
Test location Final cleaning AHERA clearance
1
2
-0.02
-0.02
-0.02
-0.02
The asbestos safety technician (AST) did not monitor the static pressure
differential across the containment barriers. Instead, ventilation smoke
tubes were used to check the negative pressure visually (i.e., direction of
airflow through openings in the containment barrier, such as the decontami-
nation facility and waste load-out port). Reportedly, these qualitative
checks were performed each morning and afternoon.
The HEPA-filtration units were placed so that the makeup air entered the
work area through the personnel decontamination facility and waste load-out
port. The three operating units were positioned along exterior walls to
facilitate venting the exhaust through windows via an interconnected flexible
duct. The discharge air from the HEPA-filtration units was not monitored for
fiber content.
The contractor, who was responsible for maintaining the HEPA-filtration
units, stated that the prefilters and secondary filters were changed before
final cleaning was initiated and the HEPA filters were changed at the begin-
ning of the project. Thereafter, the prefilters were changed daily and
secondary filters were changed when they became "visibly dirty." The HEPA
filters were changed every 600 to 700 hours (as recommended by the manu-
facturer) or when an audible alarm was actuated by a differential pressure
sensor set by the manufacturer.
FINAL CLEANING
Personal Protective Equipment
The personal protective equipment worn by the workers during final
cleaning consisted of full-body disposable coveralls and either full- or
151
-------
Percent of Nominal Airflow
in
ro
100
80
60
40
20
77%
84%
82%
HEPA Filtration Unit
(Same Model)
Figure O-1. Airflow performance for HEPA filtration systems
operating during final cleanup.
-------
Percent of Nominal Airflow
CTl
CO
100
80
60
40
20
71%
70%
77%
HEPA Filtration Unit
(Same Model)
Figure O-2. Airflow performance for HEPA filtration systems
operating during AHERA clearance.
-------
half-facepiece air-purifying respirators equipped with dual-cartridge HEPA
filters.
Cleaning Procedures
Final cleaning began after the encapsulated plastic sheeting was removed
from the walls and floors. The critical barriers, windows, doors, student
lockers, water fountains, and heating, ventilation, and air-conditioning
(HVAC) vents, etc., remained sealed. The HEPA filtration units remained in
service.
The final cleaning was organized so the workers began in the areas
farthest from the personnel decontamination facility and worked toward it.
No association appeared to exist between the work direction and the location
of the HEPA-filtration units.
Final cleaning began with the cleaning of the T-bar ceiling grid network
and hard-to-reach areas (such as indented corners and crevices) with a vacuum
equipped with a HEPA filter. The vertical and horizontal surfaces were then
sprayed with amended water. The contractor reportedly prepared the amended
water solution by mixing approximately 1 ounce each of 50 percent poly-
oxyethylene ester and 50 percent polyoxyethylene ether in 5 gallons of water.
The resultant asbestos-containing water on the floor was gathered into
pools by use of a rubber squeegee. The residual water was removed with a
wet vacuum and placed in double-layered, 6-mil-thick, asbestos-disposal bags,
which usually contained plastic that had been removed from the walls and
floors.
All of the vertical and horizontal surfaces were then wet-cleaned with
amended water. The elevated horizontal and vertical surfaces were wiped
first and then all other surfaces. All of the surfaces except the floors
were wiped with cotton rags dampened with amended water. A bucket of amended
water was either used by a single worker or shared by several workers. The
workers did not appear to wipe the surfaces in any one direction. The cloth
rags were not replaced frequently, especially during the cleaning of elevated
and hard-to-access surfaces. Nor was the amended water changed frequently.
After the walls, windows, and other surfaces (plastic-covered student
lockers, light fixtures, HEPA-filtration systems and associated exhaust
ducts, etc.) were wet-wiped, the floor was mopped with a clean mop head
wetted with amended water. No changes in the water were not observed during
this procedure.
The last step in final cleaning involved removal of the plastic sheeting
covering the HEPA-filtration units and associated exhaust ducts. The latter
were covered with a polyethylene plastic sleeve. According to the
contractor, this simplified cleaning of this equipment.
Final cleaning involved one complete wet-cleaning of the floors. No ag-
gressive cleaning [i.e., air sweeping of all vertical and horizontal surfaces
to dislodge any remaining particulate) was conducted.
154
-------
Wastewater from the wet-wiping and mopping operations was treated as
asbestos-containing water and placed in double-layered, 6-mil-thick, standard
disposal bags. These standard asbestos disposal bags which contained
wastewater were not placed in leak-tight containers or solidified with a
gelling compound. The rags and mop heads used during cleaning also were
placed in these bags. The bags were not wet-wiped with amended water before
being removed from the abatement area.
Upon completing final cleaning, the abatement contractor requested a
final visual inspection by an onsite AST, who was the building owner's
representative. The AST conducted a visual inspection within 2 hours after
notification. The AST identified several areas that required further clean-
ing, including 1) ledges along staircases, 2) indented corners, and 3) light-
ing fixtures. After these designated areas were recleaned, the AST conducted
a final walk-through inspection to assure that the identified areas were
clean.
FINAL VISUAL INSPECTION BY NEW JERSEY DEPARTMENT OF HEALTH, ASBESTOS CONTROL
SERVICE
The site failed the first visual inspection because of the presence of
debris on overhead pipes, on the grid system framework for suspended ceiling
panels, and in corners of floor-wall intersections. The site passed the
second visual inspection.
AHERA CLEARANCE SAMPLING BY AST
The AHERA clearance sampling was initiated approximately 24 hours after
the site had passed the visual inspection. Using a hand-held electric leaf
blower, the AST conducted aggressive air sweeping of vertical and horizontal
surfaces for approximately 34 minutes, which is equivalent to approximately
5 minutes per 650 ft2 of floor area or 6 minutes per 6600 ft3 of work space.
Four box-type floor fans with 18-inch blades were subsequently used to main-
tain air turbulence during sampling.
The clearance air samples were collected on 25-mm, 0.45-ym pore size,
mixed cellulose ester membrane filters contained in a three-piece cassette
with a 50-mm conductive cowl. The samples were collected at flow rates of
approximately 10 liters per minute. The laboratory report indicates that the
samples were analyzed in accordance with the AHERA mandatory TEM method.
Table 0-3 presents the results of the clearance samples the AST col-
lected inside the abatement area. The samples met the initial AHERA clear-
ance criterion, i.e., an average asbestos concentration of less than 70
structures per square millimeter (s/mm2). The average asbestos concentration
for the five inside samples was actually 0 s/mm2.
155
-------
TABLE 0-3. AHERA CLEARANCE SAMPLE RESULTS
Sample
location
Inside
Inside
Inside
Inside
Inside
Sample volume,
liters
Not reported
Not reported
Not reported
Not reported
Not reported
Asbestos
s/mm2
0
0
0
0
0
concentration
s/cm3
<0.005b
<0.005b
<0.005b
<0.005b
<0.005b
Outside samples and blanks were not analyzed because the aver-
age asbestos concentration for the five inside samples was
less than 70 s/mm2.
Sensitivity of the analytical method.
156
-------
CASE HISTORY P
SITE DESCRIPTION
This abatement project involved removal of trowel-applied, asbestos-
containing, acoustical ceiling plaster and mixed-diameter pipe insulation
from a single-story school building. The abatement area included corridors,
classrooms, and offices. The project specification indicated that the abate-
ment involved approximately 8500 ft2 of acoustical ceiling plaster containing
91 to 93 percent chrysotile and approximately 1600 linear feet of mixed--
diameter pipe insulation. The latter included hard-packed pipe insulation
(24 percent chrysotile), air-cell-paper pipe insulation (4 to 10 percent
chrysotile), and hard-packed joint insulation (60 percent chrysotile).
VENTILATION AND NEGATIVE-AIR PRESSURE
Five high-efficiency particulate air (HEPA) filtration units were oper-
ated during the final cleaning period, and four were operated during AHERA
clearance sampling. Table P-l presents the measured air-intake volume for
each unit. The average air-intake volume was 1566 ft3/min during final
cleaning and 1570 ft3/min during AHERA clearance sampling. Based on the
volume of the work area (77,000 ft3) and the combined average air-intake
volumes, the air-exchange rates were approximately 6 air changes per hour
during final cleaning and 4.9 air changes per hour during AHERA clearance
sampling.
Figures P-l and P-2 compare the measured air-intake volume for each
HEPA-filtration unit operating during final cleaning and AHERA clearance
sampling, respectively, with the unit's nominal airflow. The actual operat-
ing percentages of the nominal airflow ranged from 69 to 85 during final
cleaning and from 74 to 85 during AHERA clearance sampling.
Table P-2 presents the static pressure differential measured across the
containment barriers at two locations. The number of locations tested was
determined by available access to the critical containment barriers. The
static pressure differential ranged from -0.02 to -0.03 in. water during
final cleaning and was -0.02 in. water during AHERA clearance sampling.
The asbestos safety technician (AST) did not monitor the static pressure
differential across the containment barriers. Instead, ventilation smoke
tubes were used to check the negative pressure visually (i.e., direction of
airflow through openings in the containment barrier, such as the decontami-
nation facility and waste load-out port). Reportedly, these qualitative
checks were performed each morning and afternoon.
157
-------
TABLE P-l. AIRFLOW PERFORMANCE OF HEPA-FILTRATION UNITS
Airflow, ft /min
Model Unit Mean Min.
Max.
Std,
dev.
95% Confidence
interval
Lower Upper
Final cleaning
1
1
2
2
2
1
2
3
4
5
1596
1549
1381
1596
1706
1260
1344
1092
1428
1512
1848
1848
1680
1848
1848
171
148
163
115
93
1505
1470
1294
1535
1657
1687
1628
1467
1657
1756
AHERA clearance sampling
1
1
2
2
1
2
3
4
1502
1701
1470
1607
1344
1428
1344
1428
1680
1848
1680
1848
102
144
103
129
1447
1624
1415
1538
1556
1778
1525
1675
TABLE P-2. STATIC PRESSURE DIFFERENTIALS
ACROSS CONTAINMENT BARRIERS
(in. water)
Test location
Final cleaning
AHERA clearance
-0.03
-0.02
-0.02
-0.02
158
-------
Percent of Nominal Airflow
en
10
100-r
234
HEPA Filtration Unit
Model 1
Model 2
Figure P-1. Airflow performance for HEPA filtration systems
operating during final cleanup.
-------
Percent of Nominal Airflow
en
O
100 -Y
80
60
40 -
20 -
75%
1
m
85%
74%
2 3
HEPA Filtration Unit
Model 1
Model 2
Figure P-2. Airflow performance for HEPA filtration systems
operating during AHERA clearance.
-------
The HEPA-filtration units were placed so that the makeup air entered the
work area through the personnel decontamination facility and waste load-out
port. Three of the five operating units were positioned along exterior
walls, to facilitate venting the exhaust through windows via an inter-
connected flexible duct. The exhaust of two of the five units was vented
through a doorway via an interconnected flexible duct that passed through a
classroom outside of the abatement area. This is particularly noteworthy
because the the flexible duct for one of the two units was torn and a per-
centage of the exhaust air was released into the building. The discharge air
from the HEPA-filtration units was not monitored for fiber content.
The contractor, who was responsible for maintaining the HEPA-filtration
units, stated that the prefilters and secondary filters were changed before
final cleaning was initiated and the HEPA filters were changed at the begin-
ning of the project. Thereafter, the prefilters were changed daily and the
secondary filters were changed when they became "visibly dirty." The HEPA
filters were changed when an audible alarm was actuated by a differential
pressure sensor set by the manufacturer.
FINAL CLEANING
Personal Protective Equipment
The personal protective equipment worn by the workers during final
cleaning consisted of full-body disposable coveralls and either full- or
half-facepiece air-purifying respirators equipped with dual-cartridge HEPA
filters.
Cleaning Procedures
Final cleaning began after the plastic sheeting was removed from the
walls and floors. The critical barriers, windows, doors, chalkboards, stu-
dent lockers, and heating, ventilation, and air-conditioning (HVAC) vents
remained sealed. The HEPA filtration units remained in service.
The final cleaning was organized so the workers began in the areas
farthest from the personnel decontamination facility and worked toward it.
No association appeared to exist between the work direction and the location
of the HEPA-filtration units.
Final cleaning began with the spraying of the walls, windows, plastic
critical containment barriers, and other vertical surfaces with water to
remove any loosely bound debris. The resultant asbestos-containing water on
the floor was gathered into pools by use of a rubber squeegee. The bulk of
the pooled water was scooped up with plastic bladed shovels, an approach that
worked surprisingly well. The water was containerized in double-layered,
6-mil-thick, asbestos-disposal bags, which generally contained plastic that
had been removed from the walls and floors. Residual water removed with a
HEPA-filtered wet vacuum was also placed in these bags.
161
-------
Some of the asbestos-containing water penetrated the seams between the
vinyl floor tiles in classrooms and caused sections to buckle. Some of these
buckled floor tiles were present in each of the classrooms of the abatement
area. The asbestos-containing water beneath the floor tiles was allowed to
dry, and the tiles were not repaired. These areas could represent potential
sources of airborne asbestos fibers when repaired later by maintenance per-
sonnel .
After the surfaces had dried, a vacuum equipped with a HEPA filter was
used to clean crevices around windows, doors, baseboards, shelves, floor-wall
interfaces, etc.
All of the vertical and horizontal surfaces were then wet-cleaned with
amended water. The contractor reportedly prepared the amended water solution
by mixing approximately 2 ounces each of 50 percent polyoxyethylene ester and
50 percent polyoxyethylene ether in 5 gallons of water.
The elevated horizontal and vertical surfaces were wiped first and then
all the other surfaces. All of the surfaces except the floors were wiped
with cotton rags dampened with amended water. A bucket of amended water was
either used by a single worker or shared by several workers. The workers did
not appear to wipe the surfaces in any one direction. The cloth rags were
not replaced frequently, especially during the cleaning of elevated and
hard-to-access surfaces. Nor was the amended water changed frequently.
After the walls, windows, and other surfaces (shelves, ledges, etc.)
were wet-wiped, the floor was mopped with a clean mop head wetted with
amended water. No changes in the water were observed during this procedure.
No aggressive cleaning (i.e., air sweeping of all vertical and horizontal
surfaces to dislodge any remaining particulate) was conducted.
Wastewater from the wet-wiping and mopping operations was treated as
asbestos-containing water and placed in double-layered, 6-mil-thick, standard
disposal bags. These standard asbestos disposal bags which contained
wastewater were not placed in leak-tight containers or solidified with a
gelling compound. The rags and mop heads used during cleaning were also
placed in bags. The bags were not wet-wiped with amended water and removed
from the abatement area.
Upon completing final cleaning, the abatement contractor requested a
final visual inspection by an onsite AST, the building owner's representa-
tive. The AST conducted a visual inspection within 2 hours of notification.
The AST identified several areas that required further cleaning, including
ceiling-wall intersections and the tops of lighting fixtures. After these
designated areas were recleaned, the AST conducted a final walk-through inspection
to assure that the identified areas were clean.
162
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FINAL VISUAL INSPECTION BY NEW JERSEY DEPARTMENT OF HEALTH, ASBESTOS CONTROL
SERVICE
The site failed the first visual inspection because of the presence of
debris on pipes, in the openings where the pipes penetrated the walls, on
electrical fixtures and wires, in door jambs, at ceiling-wall junctions, on
walls, inside a fireplace and chimney, and in a sink used for disposal of
asbestos-containing waste- water. Six bulk samples were collected to char-
acterize the residual debris found in these locations. The debris found in
the fireplace had an asbestos content of 11 percent chrysotile; that found at
the ceiling-wall junction contained approximately 4 percent chrysotile. No
asbestos was identified in the sample of slurry found on a wall. Chrysotile
asbestos also was identified in debris found on the tops of doors and on
walls; however, the samples were not large enough to quantify the asbestos
content.
The site failed the second visual inspection because of debris behind
the fireplace, at ceiling-wall junctions, and on floors and residual slurry
found on walls and underneath stairs. Eight bulk samples were collected to
characterize the debris and slurry found during this inspection, and chryso-
tile asbestos was identified in all of them. The asbestos content of the
debris found at the ceiling-wall junction was approximately 6 percent. All
the other samples were not large enough to quantify the asbestos content.
The site passed the third visual inspection.
AHERA CLEARANCE SAMPLING BY AST
The AHERA clearance sampling was initiated about 2 hours after the site
had passed the visual inspection. Using a hand-held electric leaf blower,
the AST conducted aggressive air sweeping of vertical and horizontal surfaces
for approximately 30 minutes, which is equivalent to approximately 5 minutes
per 1400 ft2 of floor area. No floor fans were used subsequently to maintain
air turbulence during sampling.
The clearance air samples were collected on 25-mm, 0.45-vim pore size,
mixed cellulose ester membrane filters contained in a three-piece cassette
with a 50-mm conductive cowl. The samples were collected at flow rates of
approximately 10 liters per minute. The laboratory report indicates that the
samples were analyzed in accordance with the AHERA mandatory TEM method.
Table P-3 presents the results of the clearance samples the AST col-
lected inside the abatement area. The samples met the initial AHERA clear-
ance criterion, i.e., an average asbestos concentration of less than 70
structures per square millimeter (s/mm2). The average asbestos concentration
for the five inside samples was actually 0 s/mm2.
163
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TABLE P-3. AHERA CLEARANCE SAMPLE RESULTS
Sample
location
Inside
Inside
Inside
Inside
Inside
Sample volume,
liters
2299
2221
2270
2291
2318
Asbestos
s/mm2
0
0
0
0
0
concentration
s/cm3
<0.005b
<0.005b
<0.005b
<0.005b
<0.005b
Outside samples and blanks were not analyzed because the aver-
age asbestos concentration for the five inside samples was
less than 70 s/mm2.
Sensitivity of the analytical method.
164
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CASE HISTORY Q
SITE DESCRIPTION
This abatement project involved removal of approximately 5400 ft2 of
spray-applied asbestos-containing acoustical plaster from ceilings and
fascias on the first floor of a two-story school building. The abatement
area included corridors, classrooms, and offices. The project specification
indicated that the asbestos content of the acoustical plaster was approxi-
mately 2 to 6 percent chrysotile.
VENTILATION AND NEGATIVE AIR PRESSURE
Three high-efficiency particulate air (HEPA) filtration units were
operated during the final cleaning period, and three were operated during
AHERA clearance sampling. Table Q-l presents the measured air-intake volume
for each unit. The average air-intake volume was 1371 ft3/min during final
cleaning and 1438 ft3/min during AHERA clearance sampling. Based on the
volume of the work area (55,120 ft3) and the combined average air-intake
volumes, the air exchange rates were approximately 4.5 air changes per hour
during final cleaning and 4.7 air changes per hour during AHERA clearance
sampling.
TABLE Q-l. AIRFLOW PERFORMANCE OF HEPA-FILTRATION UNITS
Airflow, ft /min
Model Unit Mean Min.
Max.
Std.
dev.
95% Confidence
interval
Lower Upper
Final cleaning
1
1
2
1
2
3
1235
1162
1717
999
944
1596
1443
1499
1848
131
122
94
1165
1097
1667
1305
1227
1767
AHERA clearance sampling
1
1
2
1
2
3
1394
1245
1675
1221
999
1344
1491
1499
1848
98
161
124
1342
1160
1609
1447
1331
1741
165
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Figures Q-l and Q-2 compare the measured air-intake volume of each
HEPA-filtration unit operating during final cleaning and AHERA clearance
sampling, respectively, with the unit's nominal airflow. The actual
operating percentages of the nominal airflow ranged from 59 to 86 during
final cleaning and from 62 to 84 during AHERA clearance sampling.
Table Q-2 presents the static pressure differential measured across the
containment barriers at two locations. The number of locations tested was
determined by available access to the critical containment barriers. The
static pressure differential was -0.01 in. water during both final cleaning
and AHERA clearance sampling.
TABLE Q-2. STATIC PRESSURE DIFFERENTIALS
ACROSS CONTAINMENT BARRIERS
(in. water)
Test location Final cleaning AHERA clearance
1
2
-0.01
-0.01
-0.01
-0.01
The asbestos safety technician (AST) did not monitor the static pressure
differential across the containment barrier. Instead, ventilation smoke
tubes were used to check the negative pressure visually (i.e., direction of
airflow through openings in the containment barrier, such as the decontami-
nation facility and waste load-out port). Reportedly, these qualitative
checks were performed each morning.
The HEPA-filtration units were placed so that the makeup air entered the
work area through the personnel decontamination facility and waste load-out
port. The three operating units were positioned along exterior walls to
facilitate venting the exhaust through windows via an interconnected flexible
duct. The discharge air from the HEPA-filtration units was not monitored for
fiber content.
The contractor, who was responsible for maintaining the HEPA-filtration
units, stated that the prefilters and secondary filters were changed before
final cleaning was initiated and the HEPA filters were changed at the begin-
ning of the project. Thereafter, the prefilters were changed daily, and the
secondary filters were changed when they became "visibly dirty." The HEPA
filters were changed when an audible alarm was actuated by a differential
pressure sensor set by the manufacturer.
FINAL CLEANING
Personal Protective Equipment
The personal protective equipment worn by the workers during final
cleaning consisted of full-body disposable coveralls and either full- or
166
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Percent of Nominal Airflow
01
100^
80-
60
40-
20-
62%
^
86%
HEPA Filtration Unit
Model 1
Model 2
Figure Q-1. Airflow performance for HEPA filtration systems
operating during final cleanup.
-------
Percent of Nominal Airflow
en
CO
100 -
80-
60
40 -
20-
70%
62%
HEPA Filtration Unit
Model 1
Model 2
Figure Q-2. Airflow performance for HEPA filtration systems
operating during AHERA clearance.
-------
half-facepiece air-purifying respirators equipped with dual-cartridge HEPA
filters.
Cleaning Procedures
Final cleaning began after the plastic sheeting was removed from the
walls, floors, and other surfaces such as closets. The critical barriers,
windows, doors, chalkboards, and heating, ventilation, and air-conditioning
(HVAC) vents remained sealed. The HEPA filtration units remained in service.
The final cleaning was organized so the workers began in the areas
farthest from the personnel decontamination facility and worked toward it.
No association appeared to exist between the work direction and the location
of the HEPA-filtration units.
Final cleaning began with the wire-brushing of the ceiling-wall inter-
face to remove any visible debris. A vacuum equipped with a HEPA filter was
then used to clean crevices around windows, doors, shelves, stairs, floor-
wall intersections, baseboards, etc.
The walls, windows, plastic critical containment barriers, and other
vertical surfaces were then sprayed with a light water mist to remove any
loosely bound debris. The resultant asbestos-containing water on the floor
was gathered into pools by use of a rubber squeegee. The bulk of the pooled
water was scooped up with plastic-bladed shovels, a approach that worked
surprisingly well. The water was containerized in double-layered, 6-mil-
thick, asbestos-disposal bags, which usually contained plastic that had been
removed from the walls and floors. The residual water removed with a wet
vacuum was also placed in these bags.
All of the vertical and horizontal surfaces were then wet-cleaned with
amended water. The contractor reportedly prepared the amended water solution
by mixing approximately 2 ounces each of 50 percent polyoxyethylene ester and
50 percent polyoxyethylene ether in 5 gallons of water.
The elevated horizontal and vertical surfaces were wiped first and then
all the other surfaces. All of the surfaces except the floors were wiped
with cotton rags dampened with amended water. A bucket of amended water was
either used by a single worker or shared by several workers. The workers did
not appear to wipe the surfaces in any one direction. The cloth rags were
not replaced frequently, especially during the cleaning of elevated and
hard-to-access surfaces. Nor was the amended water changed frequently.
After the walls, windows, and other surfaces (shelves, ledges, tops of
closets, etc.) had been wet-wiped, the floor was mopped with a clean mop head
wetted with amended water. No changes in the water were observed during this
procedure.
No aggressive cleaning (i.e., air sweeping of all vertical and hori-
zontal surfaces to dislodge any remaining particulate) was conducted.
169
-------
Wastewater from the wet-wiping and mopping operations was treated as
asbestos-containing water and placed in double-layered, 6-mil-thick, standard
disposal bags. These standard asbestos disposal bags which contained
wastewater were not placed in leak-tight containers or solidified with a
gelling compound. The rags and mop heads used during cleaning also were
placed in these bags. The bags were not wet-wiped with amended water before
being removed from the abatement area.
Upon completing final cleaning, the abatement contractor requested a
final visual inspection by an AST, the building owner's representative. The
AST conducted a visual inspection within 2 hours after notification. The AST
identified several areas that required further cleaning,including tops of
storage closets and light fixtures, baseboard moldings, and indented corners
at window ledges. After these designated areas were recleaned, the AST con-
ducted a final walk-through inspection to assure that the identified areas
were clean.
FINAL VISUAL INSPECTION BY NEW JERSEY DEPARTMENT OF HEALTH, ASBESTOS CONTROL
SERVICE
The site failed the first visual inspection because of the presence of
debris on top of storage closets, on structural beams. The site also failed
the second visual inspection for two reasons: 1) debris in openings at wall
penetrations, and 2) debris on several light fixtures. The site failed the
third visual inspection as well because of debris found at wall-ceiling
intersections, in door jams, and in the corners of window sills. The site
passed the fourth visual inspection.
AHERA CLEARANCE SAMPLING BY AST
The AHERA clearance sampling was initiated approximately 24 hours after
the site had passed the visual inspection. Using a hand-held electric leaf
blower, the AST conducted aggressive air sweeping of vertical and horizontal
surfaces for approximately 20 minutes, which is equivalent to approximately 5
minutes per 1400 ft2 of floor area. Five box-type floor fans with 20-inch
blades were subsequently used to maintain air turbulence during sampling.
The clearance air samples were collected on 25-mm, 0.45-pm pore size,
mixed cellulose ester membrane filters contained in a three-piece cassette
with a 50-mm conductive cowl. The samples were collected at flow rates of
approximately 10 liters per minute. According to the laboratory report, the
samples were analyzed in accordance with the AHERA mandatory TEN method.
Table Q-3 presents the results of the clearance samples the AST col-
lected inside the abatement area. The samples met the initial AHERA clear-
ance criterion, i.e., an average asbestos concentration of less than 70
structures per square millimeter (s/mmz). The average asbestos concentration
for the five inside samples was actually 0 s/mm2.
170
-------
TABLE Q-3. AHERA CLEARANCE SAMPLE RESULTS
Asbestos concentration
Sample
location
Inside
Inside
Inside
Inside
Inside
Sample volume,
liters
Not reported
Not reported
Not reported
Not reported
Not reported
s/mm2
0
0
0
0
0
s/cm3
<0.005b
<0.005b
<0.005b
<0.005b
<0.005b
Outside samples and blanks were not analyzed because the aver-
age asbestos concentration for the five inside samples was
less than 70 s/mm2.
Sensitivity of the analytical method.
171
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CASE HISTORY R
SITE DESCRIPTION
This abatement project involved removal of approximately 2900 linear
feet of asbestos-containing thermal insulation from a single-story school
building. This included mixed-diameter air-cell-paper pipe insulation and
hard-pack fitting insulation. The abatement area included corridors, class-
rooms, offices, storage rooms, stairwells, and recreational rooms. The
project specification indicated that the asbestos content of the thermal
surface insulation was approximately 10 to 25 percent chrysotile.
VENTILATION AND NEGATIVE AIR PRESSURE
Eight high-efficiency particulate air (HEPA) filtration units were
operated during the final cleaning period, and nine were operated during
AHERA clearance sampling. Table R-l presents the measured air-intake volume
for each unit. The average air-intake volume was 1616 ft3/min during final
cleaning and 1501 ft3/min during AHERA clearance sampling. Based on the
volume of the work area (221,000 ft3) and the combined average air-intake
volumes, the air exchange rates were approximately 3.6 air changes per hour
during final cleaning and 3.7 air changes per hour during AHERA clearance
sampling.
Figures R-l and R-2 compare the measured air-intake volume of each
HEPA-filtration unit operating during final cleaning and AHERA clearance
sampling, respectively, with the unit's nominal airflow. The actual
operating percentages of the nominal airflow ranged from 76 to 85 during
final cleaning and from 69 to 82 during AHERA clearance sampling.
Table R-2 presents the static pressure differential measured across the
containment barriers at two locations. The number of locations tested was
determined by available access to the critical containment barriers. The
static pressure differential ranged from -0.01 to -0.02 in. water during
final cleaning and was -0.02 in. water during AHERA clearance sampling.
The asbestos safety technician (AST) did not monitor the static pressure
differential across the containment barrier. Instead, ventilation smoke
tubes were used to check the negative pressure visually (i.e., direction of
airflow through openings in the containment barrier, such as the decontamina-
tion facility) Reportedly, these qualitative checks were performed each
morning.
172
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TABLE R-l. AIRFLOW PERFORMANCE OF HEPA-FILTRATION UNITS
Model
1
1
1
1
1
1
1
1
Unit
1
2
3
4
5
6
7
8
3
Airflow, ft /min
Mean
1701
1638
1638
1638
1586
1654
1554
1517
Min.
Final
1512
1344
1344
1344
1344
1344
1344
1344
Max.
cleaning
1848
1848
1848
1848
1848
1848
1680
1848
AHERA clearance sampl
1
1
1
1
1
1
1
1
1
1
2
3
4
5
6
7
8
9
1523
1649
1376
1402
1381
1481
1607
1507
1586
1344
1512
1260
1176
1260
1260
1512
1344
1344
1764
1848
1596
1596
1512
1680
1848
1764
1848
Std.
dev.
92
129
139
107
132
114
103
147
ing
129
102
93
121
94
122
88
109
115
95% Confidence
interval
Lower
1652
1569
1564
1581
1515
1593
1499
1439
1454
1594
1326
1337
1331
1416
1559
1449
1524
Upper
1750
1707
1712
1695
1656
1714
1609
1596
1591
1703
1425
1466
1431
1545
1654
1565
1647
TABLE R-2. STATIC PRESSURE DIFFERENTIALS
ACROSS CONTAINMENT BARRIERS
(in. water)
Test location
1
2
Final cleaning
-0.01
-0.02
AHERA clearance
-0.02
-0.02
173
-------
Percent of Nominal Airflow
100
80
60
40
20
85%
82% 82% 82%
79%
83%
78%
76%
2345678
HEPA Filtration Unit
(Same Model)
Figure R-1. Airflow performance for HEPA filtration systems
operating during final cleanup.
-------
Percent of Nominal Airflow
en
100
80
60
40
20
82%
76%
80%
69% 70% 69%
74%
75%
79%
1 23456789
HEPA Filtration Unit
(Same Model)
Figure R-2. Airflow performance for HEPA filtration systems
operating during AHERA clearance.
-------
The HEPA-filtration units were placed so that the makeup air entered the
work area through the personnel decontamination facility. The nine operating
units were positioned along exterior walls to facilitate venting the exhaust
through windows via an interconnected flexible duct. The discharge air from
the HEPA-filtration units was not monitored for fiber content.
The contractor, who was responsible for maintaining the HEPA-filtration
units, stated that the prefilters and secondary filters were changed before
final cleaning was initiated and the HEPA filters were changed at the
beginning of the project. Thereafter, the prefilters and secondary filters
were changed when they became "visibly dirty." The HEPA filters were changed
when an audible alarm was actuated by a differential pressure sensor set by
the manufacturer.
FINAL CLEANING
Personal Protective Equipment
The personal protective equipment worn by the workers during final
cleaning consisted of full-body disposable coveralls and either full- or
half-facepiece air-purifying respirators equipped with dual-cartridge HEPA
filters.
Cleaning Procedures
Final cleaning began after the plastic sheeting was removed from the
walls and floors. The critical barriers, windows, doors, storage closets,
student wall lockers, and heating, ventilation, and air-conditioning (HVAC)
vents remained sealed. The HEPA filtration units remained in service.
Final cleaning was organized so the workers began in the areas farthest
from the personnel decontamination facility and worked toward it. No as-
sociation appeared to exist between the work direction and the location of
the HEPA-filtration units.
Final cleaning with dry sweeping of the floors with a garage- type
bristle broom. The dry sweeping technique was also used in a classroom with
a carpeted floor, where it appeared to pulverize some of the debris into the
carpet. The gathered debris was then removed with a HEPA-filtered vacuum.
To a limited extent, corners at floor-wall intersections were also cleaned
with a HEPA-filtered vacuum. No cleaning of elevated horizontal surfaces
(e.g., tops of ventilation ducts) with a HEPA-filtered vacuum was observed.
The vertical and horizontal surfaces were then wet-cleaned with amended
water. The contractor reportedly prepared the amended water solution by
mixing approximately 1 ounce each of 50 percent polyoxyethylene ester and 50
percent polyoxyethylene ether in 5 gallons of water.
176
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The horizontal and vertical surfaces that were wiped were limited to
those that could be reached without a step-ladder. Thus, surfaces such as
the tops of ventilation ducts were not wet-cleaned. All the surfaces except
the floors were wiped with cotton rags dampened with amended water. A bucket
of amended water was either used by a single worker or shared by several
workers. The workers did not appear to wipe the surfaces in any one direc-
tion. The cloth rags were not replaced frequently, especially during the
cleaning of elevated and hard-to-access surfaces. Nor was the amended water
changed frequently.
After the walls and other surfaces (shelves, ledges, plastic-covered
HEPA-filtration systems and associated exhaust ducts, etc.) had been wet-
wiped, the floor was mopped with a clean mop head wetted with amended water.
No changes in the water were observed during this procedure.
The last step in final cleaning involved removal of the plastic sheeting
covering the HEPA-filtration units and associated exhaust ducts. The latter
were covered with a plastic sleeve. According to the contractor, this simpli-
fied the cleaning of this equipment.
Final cleaning involved a second complete wet-mopping of the floors. No
aggressive cleaning (i.e., air sweeping of all vertical and horizontal sur-
faces to dislodge any remaining particulate) was conducted.
Wastewater from the wet-wiping and mopping operations was treated as
asbestos-containing water and placed in double-layered, 6-mil-thick, standard
disposal bags. These standard asbestos disposal bags which contained waste-
water were not placed in leak-tight containers or solidified with a gelling
compound. The rags and mop heads used during cleaning also were placed in
these bags. The bags were not wet-wiped with amended water before being
removed from the abatement area.
Upon completing final cleaning, the abatement contractor requested a
final visual inspection by an onsite AST, the building owner's representa-
tive. The AST conducted a visual inspection within 2 hours after notifi-
cation. The AST did not identify any areas that required further cleaning.
FINAL VISUAL INSPECTION BY NEW JERSEY DEPARTMENT OF HEALTH, ASBESTOS CONTROL
SERVICE
The site failed the first visual inspection because of the presence of
gross debris on top of ventilation ducts, in wall penetrations; on horizontal
surfaces; and on pipes, pipe fittings, elbows, and joints throughout the
entire containment area. Pipe insulation was also present on counters and
floor coverings. Five bulk samples were collected to characterize the resi-
dual debris noted during this inspection. The average asbestos content of
three samples collected from the pipe wrap debris contained approximately 45
percent chrysotile. The asbestos content of the debris collected from a pipe
elbow was approximately 80 percent chrysotile.
177
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The site failed the second visual inspection because of gross debris on
ventilation ducts; pipes; pipe hangers; elbows and joints; conduit; and other
horizontal surfaces. Residual debris was also found in wall penetrations
throughout the containment area. Five bulk samples were collected to
characterize the residual debris noted during the inspection. The average
asbestos content of the pipe wrap debris found in the wall penetrations was
approximately 30 percent chrysotile; the average content of that on pipe
joints and elbows was approximately 60 percent chrysotile. The asbestos
content of some debris found on top of a ventilation duct was approximately
50 percent chrysotile.
The site failed the third visual inspection because of the presence of
debris in wall penetrations and in dust on horizontal surfaces throughout the
containment area. Four bulk samples were collected to characterize the
residual debris found in the wall penetrations. The average asbestos content
of these samples was approximately 50 percent chrysotile.
The site failed the fourth visual inspection because of the presence of
debris behind lockers; on pipes, pipe joints, and elbows; on tops of venti-
lation ducts and other horizontal surfaces throughout the containment area;
and in wall penetrations. Six bulk samples were collected to characterize
the residual debris noted during the inspection. The average asbestos con-
tent of samples of debris from the tops of ventilation ducts was approxi-
mately 50 percent chrysotile. The asbestos content of the corrugated pipe
wrap found behind the student lockers was approximately 90 percent chryso-
tile.
The site failed the fifth visual inspection because of the presence of
debris on pipes, pipe elbows, and joints; on student lockers; behind coun-
ters; and on the floor at random locations throughout the containment area.
Eight bulk samples were collected to characterize the debris found behind
counters and on pipe elbows and joints. The average asbestos content of the
debris found behind the counter was about 40 percent chrysotile; the average
content of that found on pipe fittings was approximately 40 and 70 percent
chrysotile.
The site failed the sixth visual inspection because of the presence of
debris on ventilation fans and ducts, floors, horizontal surfaces, and pipe
elbows. Five bulk samples were collected to characterize the residual debris
noted on pipe elbows and ventilation ducts. Chrysotile asbestos was iden-
tified in each bulk sample; however, the samples were not large enough to
quantify the asbestos content in each.
The site passed the seventh visual inspection.
AHERA CLEARANCE SAMPLING BY AST
The AHERA clearance sampling was initiated approximately 24 hours after
the site had passed the visual inspection. Using a hand-held electric leaf
blower, the AST conducted aggressive air sweeping of vertical and horizontal
178
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surfaces for approximately 7 minutes, which is equivalent to approximately 5
minutes per 17,000 ft2 of floor area. No floor fans were used subsequently
used to maintain air turbulence during sampling.
The clearance air samples were collected on 25-mm, 0.45-ym pore size,
mixed cellulose ester membrane filters contained in a three-piece cassette
with a 50-mm conductive cowl. The samples were collected at flow rates
ranging from 11 to 12 liters per minute. The laboratory report indicates
that the samples were analyzed in accordance with the AHERA mandatory TEM
method.
Table R-3 presents the results of the clearance samples the AST col-
lected inside the abatement area. The samples met the initial AHERA
clearance criterion, i.e., an asbestos concentration of less than 70 struc-
tures per square millimeter (s/mm2). The average asbestos concentration for
the five inside samples was actually 0 s/mm2.
Sample
location
Inside
Inside
Inside
Inside
Inside
TABLE R-3. AHERA
Sample volume
liters
2040
2040
2040
2040
2040
CLEARANCE SAMPLE RESULTS
Asbestos concentration
>
s/mm2 s/cm3
0 <0.005b
0 <0.005b
0 <0.005b
0 <0.005b
0 <0.005b
Outside samples and blanks were not analyzed because the aver-
age asbestos concentration for the five inside samples was
less than 70 s/mm2.
Sensitivity of the analytical method.
179
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CASE HISTORY S
SITE DESCRIPTION
This abatement project involved removal of approximately 7200 ft2 of
trowel-applied asbestos-containing acoustical ceiling plaster from a single-
story school building. The abatement area included a gymnasium and stage,
corridors, and storage areas. The project specification indicated that the
asbestos content of the acoustical ceiling plaster was approximately 10 to 20
percent chrysotile.
VENTILATION AND NEGATIVE AIR PRESSURE
Eight high-efficiency particulate air (HEPA) filtration units were
operated during the final cleaning period, and eight were operated during
AHERA clearance sampling. Table S-l presents the measured air-intake volume
of each unit. The average air-intake volume was 1328 ft3/min during final
cleaning and 1199 ft3/min during AHERA clearance sampling. Based on the
volume of the work area (152,000 ft3) and the combined average air-intake
volumes, the air exchange rates were approximately 4.2 air changes per hour
during final cleaning and 3.8 air changes per hour during AHERA clearance
sampling.
Figures S-l and S-2 compare the measured air-intake volume of each
HEPA-filtration unit operating during final cleaning and AHERA clearance
sampling, respectively, with the unit's nominal airflow. The actual operat-
ing percentages of the nominal airflow ranged from 43 to 82 during final
cleaning and from 46 to 82 during AHERA clearance sampling.
Table S-2 presents the static pressure differential measured across the
containment barriers at two locations. The number of locations tested was
determined by available access to the critical containment barriers. The
static pressure differential ranged from -0.01 to -0.02 in. water during
final cleaning and was -0.02 in. water during AHERA clearance sampling.
The asbestos safety technician (AST) did not monitor the static pressure
differential across the containment barrier. Instead, ventilation smoke
tubes were used to check the negative pressure visually (i.e., direction of
airflow through openings in the containment barrier, such as the decontami-
nation facility and waste load-out port). Reportedly, these qualitative
checks were performed each morning and afternoon.
180
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TABLE S-l. AIRFLOW PERFORMANCE OF HEPA-FILTRATION UNITS
Model
1
1
1
1
1
1
2
2
Unit
1
2
3
4
5
6
7
8
Airflow, ft3/min
Mean
1486
1549
1649
1612
1544
1638
721
429
Min.
Final
1008
1260
1428
1344
1176
1344
571
310
Max.
cleaning
1848
1848
1848
1764
1848
1848
856
489
Std.
dev.
231
181
126
123
170
136
81
64
95% Confidence
interval
Lower
1362
1453
1582
1546
1453
1565
678
395
Upper
1609
1645
1715
1677
1634
1711
764
463
AHERA clearance sampling
1
1
1
1
1
2
2
2
1
2
3
4
5
6
7
8
1478
1633
1502
1491
1549
823
657
460
840
1344
1176
1008
1260
489
489
359
1848
1848
1848
1764
1848
978
734
571
299
122
151
225
190
134
80
56
1319
1568
1421
1371
1447
751
614
431
1638
1698
1582
1611
1650
894
700
490
TABLE S-2. STATIC PRESSURE DIFFERENTIALS
ACROSS CONTAINMENT BARRIERS
(in. water)
Test location
Final cleaning
AHERA clearance
-0.02
-0.01
-0.02
-0.02
181
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00
ro
Percent of Nominal Airflow
100
80
60 J
74%
77%
82% 81%
82%
3456
HEPA Filtration Unit
Model 1
Model 2
8
Figure S-1. Airflow performance for HEPA filtration systems
operating during final cleanup.
-------
00
u>
Percent of Nominal Airflow
100 Y
0 -^
3456
HEPA Filtration Unit
Model 1
Model 2
8
Figure S-2. Airflow performance for HEPA filtration systems
operating during AHERA clearance.
-------
The HEPA-filtration units were placed so that the makeup air entered the
work area through the personnel decontamination facility. Eight of the nine
operating units were positioned along exterior walls to facilitate venting
the exhaust through windows via an interconnected flexible duct. The exhaust
of one of the nine units was vented through a doorway via an interconnected
flexible duct that passed through a classroom outside of the abatement area.
This is particularly noteworthy because the flexible duct was torn and a
percentage of the exhaust air was released into the building. The discharge
air from the HEPA-filtration units was not monitored for fiber content.
The contractor, who was responsible for maintaining the HEPA-filtration
units, stated that the prefilters and secondary filters were changed before
final cleaning was initiated and the HEPA filters were changed at the begin-
ning of the project. Thereafter, the prefilters and secondary filters were
changed when they became "visibly dirty." The HEPA filters were changed
every 600 to 700 hours (as recommended by the manufacturer) or when an
audible alarm was actuated by a differential pressure sensor set by the
manufacturer.
FINAL CLEANING
Personal Protective Equipment
The personal protective equipment worn by the workers during final
cleaning consisted of full-body disposable coveralls and either full- or
half-facepiece air-purifying respirators equipped with dual-cartridge HEPA
filters.
Cleaning Procedures
Final cleaning began after the plastic sheeting was removed from the
walls, floors, light fixtures, and other surfaces. The critical barriers,
windows, doors, and heating, ventilation, and air-conditioning (HVAC) vents
remained sealed. The HEPA filtration units remained in service.
Final cleaning was organized so the workers began in the areas farthest
from the personnel decontamination facility and worked toward it. No
association appeared to exist between work direction and the location of the
HEPA-filtration units.
Final cleaning began with the wire-brushing of the ceiling-wall inter-
sections to remove any visible debris. These surfaces and crevices around
doors, wall fixtures, electrical conduit, floor-wall intersections, etc.,
were cleaned with a HEPA-filtered vacuum.
All of the vertical and horizontal surfaces were then wet-cleaned with
amended water. The contractor reportedly prepared the amended water solution
by mixing approximately 1 ounce each of 50 percent polyoxyethylene ester and
50 percent polyoxyethylene ether in 5 gallons of water.
184
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The elevated horizontal and vertical surfaces were wiped first and then
all the other surfaces. All of the surfaces except the floors were wiped
with cotton rags dampened with amended water. A bucket of amended water was
either used by a single worker or shared by several workers. Although the
workers did not appear to wipe the surfaces in any one direction, the sur-
faces were wiped meticulously. The cloth rags were not replaced frequently,
especially during the cleaning of elevated and hard-to-access surfaces.
Nor was the amended water changed frequently.
After the walls, windows, and other surfaces (shelves, ledges, plastic-
covered HEPA-filtration systems and associated exhaust ducts, etc.) were
wet-wiped, the floor was mopped with a clean mop head wetted with amended
water. No changes in the water were observed during this procedure.
The last step in the final cleaning effort involved removal of the
plastic sheeting covering the HEPA-filtration units and associated exhaust
ducts. The latter were covered with a plastic sleeve. According to the
contractor, this simplified the difficulty in cleaning of this equipment.
Final cleaning involved one complete wet-mopping of the floors. No
aggressive cleaning (i.e., air sweeping of all vertical and horizontal sur-
faces to dislodge any remaining particulate) was not conducted.
Wastewater from the wet-wiping and mopping operations was treated as
asbestos-containing water and placed in double-layered, 6-mil-thick, standard
disposal bags. These standard asbestos disposal bags which contained
wastewater were not placed in leak-tight containers or solidified with a
gelling compound. The rags and mop heads used during cleaning also were
placed in these bags. The bags were not wet-wiped with amended water before
being removed from the abatement area.
Upon completing final cleaning, the abatement contractor requested a
final visual inspection by an onsite AST, the building owner's representa-
tive. The AST conducted a visual inspection within 2 hours after notifica-
tion. The AST identified several areas, especially elevated horizontal
surfaces, that required further cleaning. After these designated areas were
recleaned, the AST conducted a final walk-through inspection to assure that
the identified areas were clean.
FINAL VISUAL INSPECTION BY NEW JERSEY DEPARTMENT OF HEALTH, ASBESTOS CONTROL
SERVICE
The site failed the first visual inspection because of the presence of
debris on floor surfaces, electrical wires and fixtures, behind floor mold-
ings, behind shelving units, and behind balcony seats. Seven bulk samples
were collected to characterize the debris noted during the inspection.
Chrysotile asbestos was identified in all six samples; however, the samples
were not large enough to quantify the asbestos content in each.
185
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The site failed the second visual inspection because of the presence of
minor debris on the tops of the exit sign, skylights, and stage fixtures, and
dust on the balcony floor and shelving units.
The site passed the third visual inspection.
AHERA CLEARANCE SAMPLING BY AST
The AHERA clearance sampling was initiated approximately 6 hours after
the site passed the visual inspection. Using a hand-held electric leaf
blower, the AST conducted aggressive air sweeping of vertical and horizontal
surfaces for approximately 28 minutes, which is equivalent to approximately 5
minutes per 1300 ft2 of floor area. Four pedestal-type floor fans with
18-inch blades were subsequently used to maintain air turbulence during
sampling.
The clearance air samples were collected on 25-mm, 0.45-ym pore size,
mixed cellulose ester membrane filters contained in a three-piece cassette
with a 50-mm conductive cowl. The samples were collected at flow rates of
approximately 10 liters per minute. According to the laboratory report, the
samples were analyzed in accordance with the AHERA mandatory TEM method.
Table S-3 presents the results of the AST's clearance samples collected
inside the abatement area. The samples met the initial AHERA clearance
criterion, i.e., an average asbestos concentration of less than 70 structures
per square millimeter (s/mm2). The average asbestos concentration for the
five inside samples was actually 0 s/mm2.
TABLE S-3. AHERA CLEARANCE SAMPLE RESULTS
Sample
location
Inside
Inside
Inside
Inside
Inside
Sample volume,
liters
Not reported
Not reported
Not reported
Not reported
Not reported
Asbestos concentration
s/mm2 s/cm3
0 <0.005b
0 <0.005b
0 <0.005b
0 <0.005b
0 <0.005b
Outside samples and blanks were not analyzed because the aver-
age asbestos concentration for the five inside samples was
less than 70 s/mm2.
Sensitivity of the analytical method.
186
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CASE HISTORY T
SITE DESCRIPTION
This abatement project involved removal of approximately 4100 ft2 of
spray-applied asbestos-containing acoustical ceiling plaster from a three-
story school building. The abatement area included a cafeteria and stair-
well. The project specification indicated that the asbestos content of the
acoustical ceiling plaster was approximately 10 to 25 percent chrysotile.
VENTILATION AND NEGATIVE AIR PRESSURE
Two high-efficiency particulate air (HEPA) filtration units were
operated during the final cleaning period, and three were operated during
AHERA clearance sampling. Table T-l presents the measured air-intake volume
of each unit. The average air-intake volume was 1617 ft3/min during final
cleaning and 1433 ft3/min during AHERA clearance sampling. Based on the
volume of the work area (57,000 ft3) and the combined average air-intake
volumes, the air exchange rates were approximately 3.4 air changes per hour
during final cleaning and 4.6 air changes per hour during AHERA clearance
sampling.
TABLE T-l. AIRFLOW PERFORMANCE OF HEPA-FILTRATION UNITS
Airflow, ft /min
95% Confidence
interval
Model Unit Mean Min.
Max.
dev. Lower
Upper
Final cleaning
1
1
1
2
1575
1659
1344
1428
1764
1848
131
113
1505
1599
1645
1719
AHERA clearance sampling
1
2
3
1355 1176
1559 1260
1386 1176
1680 122
1764 139
1680 163
1290
1485
1299
1419
1633
1473
Figures T-l and T-2 compare the measured in-take volume for each
HEPA-filtration unit operating during final cleaning and AHERA clearance
187
-------
sampling, respectively, with the unit's nominal airflow. The actual operat-
ing percentage of the nominal airflow ranges from 79 to 83 percent during
final cleaning and from 68 to 78 percent during AHERA clearance sampling.
Table T-2 presents the static pressure differential measured across the
containment barriers at two locations. The number of locations tested was
determined by available access to the critical containment barriers. The
static pressure differential ranged from -0.01 to -0.02 in. water during
final cleaning and from -0.02 to -0.03 in. water during AHERA clearance
sampling.
TABLE T-2. STATIC PRESSURE DIFFERENTIALS
ACROSS CONTAINMENT BARRIERS
(in. water)
Test location Final cleaning AHERA clearance
1
2
-0.02
-0.01
-0.02
-0.03
The asbestos safety technician (AST) did not monitor the static pressure
differential across the containment barrier. Instead, ventilation smoke
tubes were used to check the negative pressure visually (i.e., direction of
air flow through openings in the containment barrier, such as the decon-
tamination facility and waste load-out port). Reportedly, these qualitative
checks were performed each morning.
The HEPA-filtration units were placed so that the makeup air entered the
work area through the personnel decontamination facility and waste load-out
port. The three operating units were positioned along exterior walls to
facilitate venting the exhaust through windows via an interconnected flexible
duct. The discharge air from the HEPA-filtration units was not monitored for
fiber content.
The contractor, who was responsible for maintaining the HEPA-filtration
units, stated that the prefilters and secondary filters were changed before
final cleaning was initiated and the HEPA filters were changed at the begin-
ning of the project. Thereafter, the prefilters were changed daily, and the
secondary filters were changed when they became "visibly dirty." The HEPA
filters were changed when an audible alarm was actuated by a differential
pressure sensor set by the manufacturer.
FINAL CLEANING
Personal Protective Equipment
The personal protective equipment worn by the workers during final
cleaning consisted of full-body disposable coveralls, and either full- or
half-facepiece air-purifying respirators equipped with dual-cartridge HEPA
filters.
180
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Percent of Nominal Airflow
CD
100
80
60
40
20
79%
83%
HEPA Filtration Unit
(Same Model)
Figure T-1. Airflow performance for HEPA filtration systems
operating during final cleanup.
-------
Percent of Nominal Airflow
100
80
60
40
20
68%
78%
69%
'V
HEPA Filtration Unit
(Same Model)
Figure T-2. Airflow performance for HEPA filtration systems
operating during AHERA clearance.
-------
Cleaning Procedures
Final cleaning began after encapsulated plastic sheeting was removed
from the walls, floors, light fixtures, and other surfaces. The critical
barriers, windows, doors, and heating, ventilation, and air-conditioning
(HVAC) vents remained sealed. The HEPA filtration units remained in service.
The final cleaning was organized so the workers began in the areas
farthest from the personnel decontamination facility and worked toward it.
No association appeared to exist between work direction and the location of
the HEPA-filtration units.
Final cleaning began with the spraying of walls, windows, plastic
critical containment barriers, and other vertical surfaces with a water mist
to remove any visible debris. The resultant asbestos-containing water on the
floor was gathered into pools by use of a rubber squeegee. The bulk of the
pooled water was scooped up with plastic-bladed shovels, an approach that
worked surprisingly well. The water was containerized in double-layered,
6-mil-thick, asbestos-disposal bags, which usually contained plastic that had
been removed from the walls and floors. The residual water removed with a
wet vacuum was also placed in these bags.
All of the vertical and horizontal surfaces were then wet-cleaned with
amended water. The contractor reportedly prepared the amended water solution
by mixing approximately 1 ounce each of 50 percent polyoxyethylene ester and
50 percent polyoxyethylene ether in 5 gallons of water.
The elevated horizontal and vertical surfaces were wiped first, and then
all other surfaces were wiped. All the surfaces except the floors were wiped
with cotton rags dampened with amended water. A bucket of amended water was
either used by a single worker or shared by several workers. The workers did
not appear to wipe the surfaces in any one direction. The cloth rags were
not replaced frequently, especially during the cleaning of elevated and
hard-to-access surfaces. Nor was the amended water changed frequently.
After the walls, windows, and other surfaces were wet-wiped, the floor
was mopped with a clean mop head wetted with amended water. No changes in
the water were observed during this procedure.
No aggressive cleaning (i.e., air sweeping of all vertical and hori-
zontal surfaces to dislodge any remaining particulate) was conducted.
Wastewater from the wet-wiping and mopping operations was treated as
asbestos-containing water and placed in double-layered, 6-mil-thick, standard
disposal bags. These standard asbestos disposal bags which contained
wastewater were not placed in leak-tight containers or solidified with a
gelling compound. The rags and mop heads used during cleaning were also
placed in these bags. The bags were not wet-wiped with amended water before
being removed from the abatement area.
Upon completing final cleaning, the abatement contractor requested a
final visual inspection by an onsite AST, who was the building owner's
191
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representative. The AST conducted a visual inspection within 2 hours after
notification. The AST identified several areas, particularly tops of light-
ing fixtures, that required further cleaning. After these designated areas
were recleaned, the AST conducted a final walk-through inspection to assure
that the identified areas were clean.
FINAL VISUAL INSPECTION BY NEW JERSEY DEPARTMENT OF HEALTH, ASBESTOS CONTROL
SERVICE
The site failed the first visual inspection because of the presence of
debris on walls, floors, pipes, light fixtures, wall-ceiling junctions, and
wall penetrations. Three bulk samples were collected to characterize the
debris found during the inspection. The asbestos content of the debris
sampled from the wall penetration was approximately 4 percent chrysotile and
10 percent amosite. Chrysotile asbestos also was identified in the two
samples collected from debris in the wall-ceiling junctions; however, the
samples were not large enough to quantify the asbestos content.
The site passed the second visual inspection.
AHERA CLEARANCE SAMPLING BY AST
First Attempt
The AHERA clearance sampling was initiated approximately 24 hours after
the site passed the visual inspection. Using a hand-held electric leaf
blower, the AST conducted aggressive air sweeping of vertical and horizontal
surfaces for approximately 15 minutes, which is equivalent to approximately 5
minutes per 1400 ft2 of floor area. No floor fans were used subsequently to
maintain air turbulence during sampling.
The clearance air samples were collected on 25-mm, 0.4-pm pore size,
polycarbonate membrane filters contained in a three-piece cassette with a
50-mm conductive cowl. The samples were collected at flow rates ranging from
9 to 10 liters per minute. The laboratory report, indicates that the samples
were analyzed in accordance with the AHERA mandatory TEM method.
Table T-3 presents the results of the clearance samples the AST
collected inside the abatement area. The site failed the initial AHERA
clearance criterion, an average asbestos concentration of less than 70
structures per square millimeter (s/mm2). The mean asbestos concentration
for the inside samples was actually 159 s/mm2. Therefore, the five inside
samples were compared with the five outside samples by use of the AHERA
Z-test. The calculated Z statistic (2.44) was greater than the AHERA limit
of 1.65; therefore, recleaning was required.
Second Attempt
This AHERA clearance sampling was initiated approximately 12 hours after
the site passed the visual inspection. Using a hand-held electric leaf
192
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blower, the AST conducted aggressive air sweeping of vertical and horizontal
surfaces for approximately 10 minutes, which is equivalent to approximately 5
minutes per 2100 ft2 of floor area or 5 minutes per 28,600 ft3 of work space.
No floor fans were used subsequently to maintain air turbulence during
sampling.
TABLE T-3. AHERA CLEARANCE SAMPLE RESULTS-FIRST ATTEMPT
Sample
location
Inside
Inside
Inside
Inside
Inside
Outside
Outside
Outside
Outside
Outside
Blank
Blank
Blank
Sample volume,
liters
1713
1706
1725
1753
1742
1720
1711
1698
1638
1689
_
-
-
Asbestos
s/mm2
181
18
72
91
434
72
18
0
18
0
18
87
0
concentration
s/cm3
0.042
0.004
0.017
0.021
0.100
0.017
0.004
<0.005a
0.004a
<0.005a
_
-
-
a Sensitivity of the analytical method.
The AST collected the same number of samples and used the same sampling
and analytical methodology as during the first clearance attempt.
Table T-4 presents the results of clearance samples the AST collected
inside the abatement area. The site passed the initial AHERA clearance
criterion, i.e., an asbestos concentration of less than 70 s/mm2. The aver-
age asbestos concentration for the five inside samples was actually 52 s/mm2.
TABLE T-4. AHERA CLEARANCE SAMPLE RESULTS-SECOND ATTEMPT
Sample
location
Inside
Inside
Inside
Inside
Inside
Sample volume,
liters
1713
1706
1725
1753
1742
Asbestos concentration
s/mmz
17
70
17
70
87
s/cm3
0.004
0.016
0.004
0.016
0.020
Outside samples and blanks were not analyzed because the
average asbestos concentration for the five inside samples
was less than 70 s/mm2.
193
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TECHNICAL REPORT DATA
(Please read Instructions on the rc\ crse before completing)
1 REPORT NO.
3 RECIPIENT'S ACCESSION NO.
4 TITLE AND SUBTITLE
Observational Study of Final Cleaning and AHERA
Clearance Sampling at Asbestos-Abatement Sites in
New Jersey
5 REPORT DATE
June 30, 1989
6. PERFORMING ORGANIZATION COOE
7 AUTHOR(S)
John R. Kominsky
Ronald W. Freyberg
8. PERFORMING ORGANIZATION REPORT NO
9 PERFORMING ORGANIZATION NAME ANO ADDRESS
10 PROGRAM ELEMENT NO.
PEI Associates, Inc.
11499 Chester Road
Cincinnati, Ohio 45246
11. CONTRACT/GRANT NO
68-03-4006
12. SPONSORING AGENCY NAME AND ADDRESS
Risk Reduction Engineering Laboratory
Office of Research and Development
U.S. Environmental Protection Agency
Cincinnati. Ohio 45268
13. TYPE OF REPORT AND PERIOD COVERED
1/88-6/89
14. SPONSORING AGENCY CODE
15 SUPPLEMENTARY NOTES
Thomas J. Powers, Project Officer (513-569-7550)
16 ABSTRACT
A study was conducted during the summer of 1988 to document final cleaning
procedures and evaluate Asbestos Hazard Emergency Response Act (AHERA) clearance air-
sampling practices used at 20 asbestos-abatement sites in New Jersey. Each abatement
took place in a school building and involved removal of surfacing material, thermal
system insulation, or suspended ceiling tiles. Final cleaning practices tend to be
similar among abatement contractors. Meticulous attention to detail in cleaning
practices .is important to a successful final cleaning. Sites passing a stringent
"no-dust" criterion of a thorough visual inspection are more likely to pass the AHERA
transmission electron microscopy clearance test. AHERA sampling and analytical require-
ments and recommendations are not completely understood and followed by consultants
conducting clearance air monitoring. Matrices are provided that cross-reference case
history information on final cleaning procedures, visual inspections, and AHERA
clearance practices at these sites.
17
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b.lDENTIFIERS/OPEN ENDED TERMS C. COSATI Field/GtOUp
18. DISTRIBUTION STATEMENT
19 SECURITY CLASS (This Report J
21. NO OF PAGES
20 SECURITY CLASS (This page/
22 PRICE
EPA Form 2220-1 (Rev. 4-77) PREVIOUS EDITION is OBSOLETE
194
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