VISUAL INSPECTION AND AHERA CLEARANCE
AT ASBESTOS ABATEMENT SITES
by
John R. Kominsky1, Ronald W. Freyberg1, James A. Brownlee2, Donald R. Gerber2,
Thomas J. Powers3, Roger C. Wilmoth3
For Presentation at the
National Asbestos Council Conference
New Orleans, LA
February 19-22, 1991
1IT Environmental Programs, Inc., Cincinnati, OH 45246;
2New Jersey Department of Health, Trenton, NJ 08625;
3U.S. Environmental Protection Agency, Risk Reduction Engineering Laboratory,
Cincinnati, OH 45268
The NJDOH-ACS inspector first visually examined all substrate surfaces to ensure
that no asbestos-containing material (ACM) remained. Special attention was given to
pipes, structural members, 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 was conducted before another visual inspection was,conducted.
The ACS inspector then determined if the worksite had been adequately cleaned. All
surfaces were examined for dust and debris, especially overhead areas (such as the
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tops of suspended light fixtures) 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. Use of a damp cloth to collect dust from the surface and then inspecting
the cloth for evidence of dust.
2. Darkening of the room and shining a flashlight so that the light beam just
glances 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
required that the entire work area be recleaned before its reinspection.
Air Sampling
After the site passed the NJDOH-ACS visual inspection, an Asbestos Safety
Technician (AST) collected AH ERA clearance air samples (which were used to declare
the site clean and to release the abatement contractor). The AST is certified by the
New Jersey Department of Community Affairs and is an employee of an Asbestos
Safety Control Monitor (ASCM) firm, that is employed by the School District or Local
Education Agency.
Concomitant air sampling was conducted by the EPA at approximately the same
time and location (within a radius of 5 feet) of the ASCM firm's sampling. The EPA
collected five area air samples in each of three locations: the abatement work area,
the perimeter area outside the abatement area but inside the building, and outdoors.
In the abatement work area, the samples were collected under the sampling
conditions created by the ASCM for AHERA clearance. The perimeter area samples
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were collected under static conditions (i.e., the activity in the area was minimal, and
the heating, ventilation, and air-conditioning system was not operating).
Sampling Methodology
The air samples were collected on open-face, 25-mm diameter, 0.45-Mm pore-
size, mixed cellulose ester (MCE) membrane filters with a 5-nm pore-size, MCE
backup diffusing filter and cellulose support pad contained in a three-piece cassette.
The filter cassettes were positioned approximately 5 feet above the floor on tripods,
with the filter face at an approximately 45-degree angle toward the floor. The filter
assembly was attached to a 1/6-hp electric-powered vacuum pump operating at a flow
rate of approximately 9 L/min. The sampling pumps were calibrated with a precision
rotameter both before and after sampling. The precision rotameter was calibrated in
the field with a primary air flow standard.
Analytical Methodology
The MCE membrane filters were prepared and analyzed in accordance with the
nonmandatory TEM method, as described in the AH ERA rule. For each sample, a
sufficient number of grid openings were analyzed to ensure a sensitivity (the
concentration represented by a single structure) of no greater than 0.005 asbestos
structure per cubic centimeter (s/cm3) of air sampled. In addition to the requirements
of the nonmandatory TEM method, the specific length and width of each structure
were measured and recorded.
AHERA TEM Clearance Test
The AHERA TEM clearance criterion is primarily comparative in nature; i.e., it is
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based on a comparison of airborne asbestos concentrations inside the abatement
work area with those outside the abatement work area but not necessarily outside the
building.4 Although inside samples may be collected as a basis for comparison when
air intake to the abatement site is primarily from other areas of the building, outdoor
samples are normally recommended because they are less likely to be affected by
work practices that might contaminate other areas inside the building.
The AHERA clearance test requires the collection of a minimum of five samples
inside and five samples outside the abatement work area. A statistical test (the Z-test)
is then used to determine if the average concentration inside the abatement area is
higher than the average concentration outside. The Z-test is carried out by the
following equation:
Y.-Y
z- ** °
o .
where Yj = the average of the natural log of the inside samples
Y0 = the average of the natural log of the outside samples
nf = the number of samples collected inside the work area
n0 = 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 AHERA clearance test
and is considered acceptable for reoccupancy.
The AHERA Z-test is preceded by two preliminary tests-an initial screening test
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and a blank contamination test. The initial screening test compares the average
concentration of the five samples collected inside the abatement area against a value
of 70 structures per square millimeter (s/mm2). If the average concentration is less
than or equal to 70 s/mm2, the work area passes the clearance test without the
analysis of the outside samples being required. If the work area samples do not pass
this initial screening test, a minimum of three blanks (filters through which no air has
been drawn) are analyzed to check for the possibility of filter contamination that would
distort the test results. If the filter concentrations are less than or equal to 70 s/mm2,
they are considered indistinguishable from blank contamination levels. If the three
blanks pass the 70 s/mm2 criterion, the outside samples are then analyzed and the Z-
test is used to compare the results with those of the samples collected inside the work
area.
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RESULTS
Site Descriptions
Fourteen of the 15 abatement projects involved general occupancy areas
(classrooms, offices, recreational rooms, and corridors), and one involved both
general occupancy areas and a boiler room. The ACM abated at nine of the sites
involved surfacing material (sprayed- or troweled-on), three involved thermal system
insulation, two involved both surfacing material and thermal system insulation, and one
involved suspended ceiling tiles. The ACM contained chrysotile asbestos (from 2% to
93%) at 14 sites and amosite asbestos (from 5% to 10%) at one site.
Final Visual Inspection
From one to seven visual inspections were conducted at the 15 abatement
sites. Figure 1 shows the percentage of sites that passed the NJDOH-ACS visual
inspection per given attempt. The largest percentage (33.5%) of sites passed the
visual inspection on the second attempt. It should be noted that final cleaning
activities were completed by the abatement contractor at all of the sites. The data
clearly indicates that the visual inspection by the NJDOH-ACS revealed the inadequacy
of the final cleaning activities for the first attempt. Additional attempts were necessary
to successfully pass the NJDOH-ACS visual inspection. The cumulative percentages
of sites passing the visual inspection were as follows: 40% by the first and second
attempts, 66.7% by the third attempt, and 93.4% by the fourth attempt.
8
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30-
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attempt.
Table 1 lists the reasons why sites failed the NJDOH-ACS inspectors's visual
inspections at the 15 sites. Fourteen of the 15 sites failed the 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 hangers. The next most
common reason was debris on floors, on horizontal surfaces, and in wall penetrations.
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Relationship Between Visual Inspection andAHERA Clearance Test
Table 2 summarizes the number of visual inspections and AH ERA TEM
clearance test results based on the U.S. EPA air sampling for each of the 15 sites.
The clearance results are presented based on the initial screening criterion, and based
on the Z-test comparison of the airborne concentration of asbestos in the abatement
area to that in the perimeter area (outside the abatement area, but inside the building)
and outdoors.
After passing a final visual inspection by the NJDOH-ACS, 27 percent (4 of 15) of
the sites passed the AHERA clearance test based on the initial screening criterion, i.e.,
the average filter concentration for the five samples collected inside the abatement
area was <70 s/mm2. Including these four sites, 53 percent (8 of 15) passed using
the perimeter area and 46 percent (7 of 15 sites) passed using outdoors as the
clearance reference point for the Z-test, respectively. It's apparent that failing the initial
screening test does not infer that the site would fail the Z-test. This situation was
observed at Sites B, C, H, and S.
These data demonstrate that final visual inspection is necessary to determine the
completeness of an abatement action and the thoroughness of cleaning the worksite;
i.e., the absence of debris, residue, or dust on surfaces. As noted in the low pass rate
of the initial visual inspection, the meticulous and conscientious inspection of surfaces
is necessary to determine the absence of debris, residue, and dust. Presumably, if
such an inspection had not been conducted at these 15 abatement sites, a higher
percentage of sites would have failed the AHERA TEM clearance test on the first
11
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attempt. Final clearance air sampling, as described in the AHERA rule, is ultimately
necessary to determine that an abatement site is acceptable for re-occupancy.
TABLE 2. RELATIONSHIP BETWEEN VISUAL INSPECTION
AND AHERA CLEARANCE TEST
Number of Initial
Visual Screening Z-test
Site Inspections Test Perimeter Outdoor
A 4 PASS PASS PASS
B 3 FAIL PASS FAIL
C 1 FAIL PASS PASS
H 2 FAIL PASS PASS
I 4 FAIL FAIL PASS
K 4 FAIL FAIL FAIL
L 2 FAIL FAIL FAIL
M 3 FAIL FAIL FAIL
N 2 FAIL FAIL FAIL
O 2 PASS PASS PASS
P 3 PASS PASS PASS
Q 4 FAIL FAIL FAIL
R 7 PASS PASS PASS
S 3 FAIL PASS FAIL
T 2 FAIL FAIL FAIL
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CONCLUSION
This paper examined the relationship between passing a thorough final visual
inspection and the AH ERA TEM clearance Z-test. A final visual inspection is
necessary to determine completeness of an abatement action and thoroughness of
the cleaning of the worksite, but can not be substituted in lieu of final clearance air
sampling.
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REFERENCES
1. Kominsky, J. R., R. W. Freyberg, J. A. Brownlee, J. H. Lucas, D. R. Gerber.
Observational Study of Final Cleaning and AH ERA Clearance Sampling at
Asbestos-Abatement Sites in New Jersey. U.S. Environmental Protection Agency,
EPA/600/S2-89/047, July, 1989.
2. U.S. Environmental Protection Agency. Guideline for Controlling Asbestos-
Containing Materials in Buildings. EPA 560/5-85-024, June 1985.
3. American Society for Testing Materials. Standard Practice for Visual Inspection of
Asbestos Abatement Projects. ASTM E1368, ASTM, 1916 Race Street,
Philadelphia, PA 19103.
4. U.S. Environmental Protection Agency. Guidelines for Conducting the AHERA TEM
Clearance Test to Determine Completion of an Asbestos Abatement Project. EPA
560/5-89-001, May, 1989.
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