United States
Environmental Protection
Agency
Risk Reduction Engineering
Laboratory
Cincinnati OH 45268
Research and Development
EPA/600/S2-90/053 Apr. 1991
EPA Project Summary
Evaluation of Two Cleaning
Methods for Removal of
Asbestos Fibers from Carpet
John R. Kominsky, Ronald W. Freyberg, Jean Chesson, and Eric J. Chatffeld
The effectiveness of dry-vacuuming
and wet-cleaning for the removal of as-
bestos fibers from carpet was examined,
and the potential for fiber reentrainment
during carpet cleaning activities was
evaluated. Routine carpet cleaning op-
erations were simulated by using high-
efficiency particulate air (HEPA) filtered
dry vacuum cleaners and HEPA-f iltered
hot-water extraction cleaners on carpet
artificially contaminated with asbestos
fibers. Overall, wet-cleaning with a hot-
water extraction cleaner reduced the level
of asbestos contamination In the carpet
by approximately 70%. There was no
significant change in carpet asbestos
concentration after dry-vacuuming. The
level of asbestos contamination had no
significant effect on the difference be-
tween the asbestos concentrations be-
fore and after cleaning. Airborne asbes-
tos concentrations were two to four times
greater during than before the carpet
cleaning activities. Neither the level of
asbestos contamination in the carpet
nor the type of cleaning method used
greatly affected the difference between
the airborne asbestos concentration
before and during cleaning.
This Project Summary was developed
by EPA's Risk Reduction Engineering
Laboratory, Cincinnati, OH, to announce
key findings of the research project that
Is fully documented In a separate report
of the same title (see Project Report
ordering Information at back).
Introduction
Buildings that contain friable asbestos-
containing materials (ACMs) may present
uncommon exposure problems for custo-
dial workers. Under certain conditions, as-
bestos fibers can be released from fire-
proofing, acoustical plaster, and other sur-
facing material. The episodic release of
asbestos from aging and deteriorating ACM
relates to several factors, such as the con-
dition and amount of asbestos present, the
accessibility of the material, activity within
the area, vibration, temperature, humidity,
airflow, use patterns, etc. Of major concern
is the extent to which carpet and furnishings
may be serving as reservoirs of asbestos
fibers and what happens to these fibers
during normal custodial cleaning operations.
The Asbestos Hazard Emergency Re-
sponse Act (AHERA) requires that all carpet
in areas of school buildings in which ACMs
are present be cleaned with either a HEPA-
filtered vacuum cleaner or a hot-water ex-
traction cleaner ("steam-cleaner"). Little
quantitative information is available on how
well these cleaners remove asbestos fibers
from carpet or on the potential for
reentrainment of airborne asbestos fibers
during these carpet cleaning activities.
The report summarized here evaluates
the concentration of asbestos fibers In the
carpet before and after cleaning for each of
the two cleaning methods and summarizes
the air monitoring results obtained during
cleaning. A separate EPA report entitled
"Asbestos Fiber Reentrainment During Dry
Printed on Recycled Paper
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Vacuuming and Wet Cleaning of Asbestos-
Contaminated Carpet" contains a complete
description of the air monitoring portion of
the study.
Study Design
Test Facility
This study was conducted in an unoccu-
pied building at Wright-Patterson Air Force
Base in Dayton, Ohio. Two rooms, each
containing approximately 500 ft2 of floor
. space, were constructed in a large bay of
the building.
The rooms were constructed of 2- x 4-in.
lumber with studs spaced on 24-in. centers
and3/4-in.plywoodfloors.Theceiling,floor,
and wails were double-covered with 6-mil
polyethylene sheeting. (The interior layer of
polyethylene sheeting was encapsulated
and replaced after each experiment.) Where
separatesheetsofpolyethylenewere joined,
the sheets were overlapped at least 12 in.
and joined with an unbroken line of adhe-
sive to prohibit air movement. Three-inch-
wide tape was then used to seal the joint
further on both the inside and outside of the
plastic sheeting.
Entry from one room to another was
through a triple-curtained doorway consist-
ing of two overlapping sheets of 6-mil poly-
ethylene placed over a framed doorway;
each sheet was secured along the top of the
doorway, and the vertical edge of one sheet
was secured along one side of the doorway
and the vertical edge of the other sheet,
atong the opposite side of the doorway.
Room size (approximately 29 x 17x 7.5ft)
was based on the minimum amount of time
required to vacuum or wet-clean the room
and to attain an adequate volume of sample
air to achieve a specified analytical sensi-
tivity. A 52-in., ceiling-mounted, axial-flow,
propeller fan was installed in each room to
facilitate air movement and to minimize
temperature stratification.
Separate decontamination facilities for
workers and waste materials were con-
nected tothe experimental areas. The worker
decontamination facility consisted of three
totally enclosed chambers: an equipment-
change room, a shower room, and a clean
change room.
Air Filtration
HEPA filtration systems were used to
reduce the airborne asbestos concentra-
tions to background levels after each ex-
periment. These units were operated during
both preparation and decontamination of
the test rooms. The air filtration units did not
operate during the carpet cleaning phase of
each experiment.
One HEPA filtration system was dedi-
cated to each test room. Each unit provided
approximately eight air changes every 15-
min period. The negative pressure inside
the test rooms ranged from-0.08 to-0.06 in.
of water. All exhaust air passed through a
HEPA filter and was discharged to the out-
doors. All makeup air was obtained from
outside the building through a window lo-
cated on the opposite side of the building
from the exhaust for the HEPA filtration
systems.
Experimental Design
Experiments 1 Through 16
Two carpet cleaning methods, dry-vacu-
uming with a HEPA-filtered vacuum and
wet-cleaning with a HEPA-filtered hot-water
extraction cleaner, were evaluated on car-
pet artificially contaminated at two different
levels—approximately 100 million and 1
billion asbestos structures per square foot
(s/ft2). Each combination of cleaning method
and contamination level was replicated four
times. Four different (same model) HEPA-
filtered vacuums and four different (same
model) HEPA-filtered hot-water extraction
units were used so the results would not be
influenced by the peculiarities of a single
unit. Each machine was used only once per
combination of cleaning method and con-
tamination level. This experimental design
yielded a total of 16 experiments.
Work-area air samples were collected to
establish airborne asbestos concentrations
before and during cleaning. For each ex-
periment, three air samples were collected
before and three during cleaning. In each
test room, the air samplers were positioned
in a triangular pattern. A total of 96 air
samples were collected.
Bulk carpet and microvacuum samples
were collected to establish the pre- and
post-cleaning carpet contamination levels.
During each experiment, six samples were
collected before and six after cleaning. A
total of 192 bulk carpet samples and 192
microvacuum samples were collected.
Two experiments were conducted each
day of the study. Each combination of
cleaning method and contamination level
was tested twice in each test room. A single
experiment consisted of contaminating a
new piece of carpet (approximately 500 ft2)
with asbestos fibers, collecting work-area
air samples, collecting microvacuum and
bulk carpet samples, dry-vacuuming orwet-
cleaning the carpet while collecting a sec-
ond set of work-area air samples, collecting
a second set of microvacuum and bulk
carpet samples, removing the carpet, and
decontaminating the test room. Each test
room was decontaminated by encapsulat-
ing the carpet and the polyethylene sheet-
ing on the ceiling and walls before their
removal. These materials were removed
and replaced after each experiment.
Experiments 17 Through 24
To evaluate the differences in the asbes-
tos-retention characteristics of new carpet
versus new carpet that has been wet-
cleaned, eight additional experiments were
conducted. These experiments were de-
signed for comparison with Experiments 1
through 16.
Experimental procedures for this second
set of experiments were identical to those in
the first 16 except that the carpet was dry-
vacuumed, wet-cleaned, and then dry-
vacuumed again when dry. The same test
area was also used; however, the two 500-
ft2 test rooms were converted to four 160-ft2
test rooms, each with dimensions of ap-
proximately 8 x 20 ft.
Each of the two cleaning methods was
tested at two carpet contamination levels
(100 million and 1 billion s/ft2). Each clean-
ing method was tested twice in two different
rooms. The same four HEPA-filtered dry
vacuums and hot-water extraction cleaners
were used. Each machine was used only
once per cleaning method and contamina-
tion level combination. This experimental
design yielded a total of eight experiments.
Bulk carpet and microvacuum samples
were again collected to establish the pre-
and post-cleaning carpet contamination
levels. During each experiment, four
samples were collected before and four
after carpet cleaning. During each experi-
ment, a total of 32 bulk samples were col-
lected. No work-area air samples were col-
lected during these eight experiments.
A single experiment consisted of dry-
vacuuming, wet-cleaning, and dry-vacu-
uming again a new piece of carpet in a
previously cleaned room;contaminating the
carpet with asbestos fibers; collecting
microvacuum and bulk carpet samples; dry-
vacuuming or wet-cleaning the carpet; col-
lecting a second set of microvacuum and
bulk carpet samples; removing the carpet;
and decontaminating the test room. Decon-
tamination methods were the same as for
Experiments 1 through 16.
Preliminary Sampling and
Analytical Performance Study
Preliminary experiments were conducted
to document the performance of the
microvacuum sampling and sonic extrac-
tion techniques for recovering the asbestos
from the carpet. The mean asbestos re-
covery from carpet contaminated with 1
billion s/ft2 was 23 million s/ft2 with
microvacuuming and 794 million s/ft2 with
sonic extraction. The coefficient of variation
(CV) for the microvacuuming techniques
was 166%, whereas the CV for the sonic
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extraction technique was 43%. Because
the sonic extraction method was clearly
superior for determining carpet contamina-
tion levels, the microvacuum samples were
not analyzed.
The preliminary experiments provided
information regarding the variability associ-
ated with this analytical technique, which
was not available when the sampling strat-
egy was being developed. The original
sample size calculations for this study as-
sumed a CV of 100% with this method,
whereas the calculated CV was 43%. This
information permitted thenumber of samples
needed to achieve statistical significance to
be modified downward, which greatly re-
duced analytical costs and analytical turn-
around time for this study.
Materials and Methods
A survey of 14 General Service Adminis-
tration (GSA) field offices in 11 States dis-
tributed across the country provided infor-
mation for the selection of the carpet and
cleaning equipment to be used in this study.
When the GSA offices lacked the needed
information with regard to wet-cleaning
equipment, six trade organizations were
contacted for recommendations concern-
ing a HEPA-filtered hot-water extraction
cleaner.
Selection of Carpet
The carpet of choice was first-grade, 100%
nylon, with 0.25-in. cut pile, 28 oz of yarn/ft2,
and dual vinyl backing.
Selection of Carpet Cleaning
Equipment
HEPA-Filtered Vacuum
The HEPA-filtered vacuum of choice was
a unit with an airflow capacity of 87 ft3/min,
a suction power of 200 watts, and 75 in.
static waterlift. This unit was also equipped
with a motor-driven carpet nozzle with a
rotating brush
HEPA-Filtered Hot-Water
Extraction Cleaner
The hot-water extraction unit of choice
was equipped with a HEPA-filtered power
head with a moisture-proof, continuous-
duty, 2-horsepower vacuum motor that de-
veloped a 100-in. static waterlift. This unit
was also equipped with an extractor tool
that uses a motor-driven cylindrical nylon-
bristle brush, 4 in. fn diameter and 14 in.
long, to agitate and scrub the carpet during
the extraction process.
Sampling Methodology
Bulk Carpet Samples
A 4-in.2 template and a utility razor knife
were used to collect carpet samples before
and after cleaning. Each carpet sample was
cut in half to provide a duplicate sample for
archiving. Each piece was placed in a sepa-
rate, labeled, wide-mouth, polyethylene jar
with a polypropylene screw cap. The tem-
plate and utility razor were thoroughly
cleaned before each experiment to avoid
cross-sample contamination.
Microvacuum Samples
Microvacuum samples were collected by
vacuuming a 100-cm2area of carpet with a
membrane filter air-sampling cassette and
a vacuum pump. The sampling assembly
consisted of a 25-mm-diameter, 0.45-u.m-
pore-size, mixed cellulose ester filter con-
tained in a three-piece cassette connected
to a sampling pump with flexible tubing.
The pump and cassette assembly was
calibrated to 10 L/min. The 100-cm2 area was
vacuumed by dragging the filter cassette
across the carpet to agitate the carpet pile.
The carpet was vacuumed for 30 sec in one
direction and another 30 sec in a direction
90 degrees to the first. After 1 min of vacu-
uming, the pump was turned off and the
filter cassette was labeled and sealed.
Air Samples
Air samples were collected on open-face,
25-mm-diameter, 0.45-n.m pore-size, mixed
cellulose ester membrane filters with a 5-
\im pore size, mixed cellulose ester backup
diffusing filter and cellulose ester support
pad contained in a three-piece cassette.
The filter cassettes were positioned ap-
proximately 5 ft above the floor with the filter
face at approximately a 45-degree angle
toward the floor. The filter assembly was
attached to an electric-powered vacuum
pump operating at a flow rate of approxi-
mately 10 L/min. Air samples were collected
for 65 min before and during carpet cleaning
to achieve a minimum air volume of ap-
proximately 650 L.
Analytical Methodology
Bulk Carpet Samples
A sonication procedure developed by
McCrone Environmental Services, Inc., was
used to extract asbestos particles from the
bulk carpet samples for subsequent analy-
sis by transmission electron microscopy
(TEM). Asbestos structures were identified
and counted as specified in EPA provisional
method, Level II.
Microvacuum Samples
The mixed cellulose ester filters used to
collect the microvacuum carpet samples
were analyzed by TEM. These samples
were prepared according to the analytical
laboratory's Standard Operating Procedure
for dust sample collection. Asbestos struc-
tures were identified and counted as speci-
fied in the EPA provisional method, Level It.
Air Samples
The mixed cellulose ester filters were
analyzed by TEM. These filters were pre-
pared and analyzed in accordance with the
nonmandatory TEM method as described
in the Asbestos Hazard Emergency Re-
sponse Act (AHERA) final rule (52 CFR
41821).
Statistical Analysis
Carpet Samples
For each experiment, a single estimated
concentration was obtained before and af-
ter cleaning by taking the arithmetic mean of
the individual estimates. This gave 24 pairs
of concentrations, one for each experiment.
The natural logarithm of each of the 48
concentrations was used for subsequent
statistical analyses. This is equivalent to
assuming that the data follow a lognormal
distribution.
The geometric mean and a 95% confi-
dence interval were calculated for each
contamination level and cleaning method. A
three-way analysis of variance (ANOVA)
with contamination level; (low;, high), clean-
ing: method, (wet, dry), and experimental set
(1 to 16,17 to 24) as the three experimental
factors was performed on the difference (on
the log scale) between the concentration
before cleaning and the concentration after
cleaning. (The difference on the log scale is'
equivalent to the ratio on the original scale.)
A 95% confidence interval for the difference
in concentration before and after cleaning
was calculated using the error mean square
of the ANOVA. Results were transformed
back to the original scale for reporting pur-
poses.
Air Samples
Airborne asbestos concentrations were
determined before and during carpet clean-
ing to study the effect of the cleaning method
and contamination loading on fiber
reentrainment during carpet cleaning. Three
work-area samples were collected before
and during carpet cleaning for each experi-
ment. A single estimate of the airborne
asbestos concentrations before and during
cleaning was then determined by averag-
ing the three respective work-area samples.
The natural logarithm of each of the con-
centrations was usedforsubsequent statis-
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tical analyses. This is equivalent to assum-
ing that the data follow a log normal distri-
bution. A two-factor ANOVA with cleaning
method (wet, dry) and contamination level
(low, high) as the experimental factors was
performed on the difference (on the log
scale) between the concentration before
cleaning and the concentration during
cleaning.
Carpet Contamination
Selected levels of carpet contamination
for this study were based on field data
collected from buildings in which ACMs
were present. Asbestos concentrations in
contaminated carpet ranging from approxi-
mately 8,000 s/ft2 to 2 billion s/ft2 were de-
tected by use of a microvac technique. Bulk
sample sonication of the samples revealed
levels ranging from 30 million to 4 billion s/
ft2. Based on these preliminary results, the
target experimental asbestos contamination
levels of approximately 100 million and 1
billion s/ft2 were believed to represent likely
carpet contamination in buildings where
ACMs are present.
Sealed ampules of fiberdispersions were
prepared spthatthe contents of one ampule
dispersed in 6 L of freshly distilled water
would provide the concentration of suspen-
sion required for artificial contamination of
one 500-ft2 sample of carpet. Calculations
of the amount of chrysolite required were
based on the assumption that all of the
fibers needed to contaminate one carpet
sample could be contained in a volume of
50 mL sealed in one ampule.
Application of Dispersion to
Carpet
A meticulously cleaned hand-pumped
garden sprayer was used to apply the as-
bestos dispersion to the carpet. The desired
controlled spray was experimentally deter-
mined by trial and error before the tests with
asbestos began. The pressure was kept
within the desired range by adding a fixed
number of pump strokes after each fixed
area was sprayed in a predetermined pat-
tern by following a grid work of string placed
overthecarpetbeforethebeginningofeach
experiment. The tank was periodically agi-
tated to help keep the asbestos fibers sus-
pended. Dehumidifiers were placed in the
room overnight to aid in drying the carpet.
The following day a 200-lb steel lawn roller
was rolledoverthecarpet surf aceto simulate
the effects of normal foot traffic in working
the asbestos into the carpet.
Carpet Cleaning Technique
The carpet was vacuumed orwet-cleaned
for a period of approximately 65 min to allow
the collection of a sufficient volume of air
samples to obtain an analytical sensitivity of
0.005 s/cm3 of air. The carpet was cleaned
in two directions, the second at a 90-degree
angle to the first.
Table 1. For each experiment, a single esti-
mated concentration before and after cleaning
was obtained by taking the arithmetic mean
of the three individual estimates. This gave
t 700
0>
•° 600
g 500
100
I Before
i After
Wet Clean Dry Vacuum
Low Contamination
Wet Clean Dry Vacuum
High Contamination
Figure 1. A verage asbestos carpet contamination before and after cleaning.
Table 1. Summary Statistics for Asbestos Concentrations in Carpet Before and After Cleaning
Approximate
Contamination
Level, s/ft2
HEPA-Filtered
Cleaner
Number
of Data
Points'
Geometric
Mean,
million s/ff
95%
Confidence
Interval
100 Million:
Before
cleaning
After
cleaning
1 Billion:
Before
cleaning
After
cleaning
Hot-water extraction 6
Dry-vacuum 6
Hot -water extraction 6
Dry-vacuum 6
Hot-water extraction 6
Dry-vacuum 6
Hot-water extraction 6
Dry-vacuum 6
62
47
18
56
589
535
196
447
(39, 101)
(37, 59)
(8,43)
(38, 83)
(397, 873)
(356, 803)
(85, 449)
(240, 832)
'Each data point represents the average of three carpet samples.
Results and Discussion
Carpet Samples
Figure 1 illustrates the average (geomet-
ric mean) concentrations of asbestos struc-
tures in the carpet before and after cleaning.
The 95% confidence intervals for the geo-
metric mean concentrations are given in
24 pairs of concentrations, one for each ex-
periment.
Results of a three-factor ANOVA indicated
no significant difference between the results
from Experiments 1 through 16 and Experi-
ments 17 through 24 (p=0.7). The difference
between the two sets of experiments was
that the carpet in Experiments 17 through 24
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Table 2. Estimated Asbestos Concentration in Carpet After Cleaning as a Proportion of the Con-
centration Before Cleaning
Approximate
Contamination
Level, s/ft?
100 Million
1 Billion
HEPA-Filtered
Cleaner
Hot-water extraction
Dry-vacuum
Hot-water extraction
Dry-vacuum
Concentration After
Cleaning as a
Proportion of
Concentration Before
Cleaning
0.29
1.19
0.33
0.84
95%
Confidence
Interval
(0.16,0.51)
(0.68,2.11)
(0.19,0.59)
(0.47, 1.48)
was first dry-vacuumed, then wet-cleaned,
and then dry-vacuumed again before con-
tamination. Thedata from all24experiments
were treated equally and reanalyzed by
using a two-factor ANOVA.
Thetype of cleaning method had asignifi-
cant effect (p<0.001) on the difference be-
tween the asbestos concentrations before
and after cleaning. The level of asbestos
contamination in the carpet, however, had
no significant effect (p=0.622). The esti-
mated asbestos concentration in the carpet
after cleaning, expressed as a proportion of
the asbestos concentration before clean-
ing, is given in Table 2, together with a 95%
confidence interval.
The asbestos concentration in the carpet
after wet-cleaning was approximately 0.3 of
the asbestos concentration before cleaning
in both the high and low contamination
levels. The upper 95% confidence limit
(Table 2) at each contamination level is less
than 1, which indicates that this reduction is
statistically significant.
The asbestos concentration in the carpet
after dry-vacuuming was 1.2 and 0.8 times
the asbestos concentration before cleaning
in the low- and high-contamination levels,
respectively. The 95% confidence intervals
for both estimates include 1, which indi-
cates that the data do not provide statisti-
cally significant evidence of either an in-
crease or a decrease in asbestos concen-
tration after dry-vacuuming.
The TEM analysis of the 144 carpet
samples before and after cleaning yielded a
total of 8,101 asbestos structures. Of these,
8,080 (99.7%) were chrysotile and 21 (0.3%)
were amphibole. The structure morphology
distribution for the particles in the carpet
samples is summarized in Table 3.
For carpet contaminated with 100 million
s/ft2, larger residual particles were consis-
tently observed in the carpet afterdry-vacu-
umingthanafterwet-cleaning. Fiber lengths
of the residual asbestos in the carpet after
dry-vacuuming and wet-cleaning carpet
contaminated with 1 billion s/ft2 were com-
parable. The reason for the difference in
results between the two contamination lev-
els is unknown.
Air Samples
Airborne asbestos concentrations were
determined before and during carpet clean-
ing in Experiments 1 through 16 to study the
effect of the cleaning method and contami-
nation loading on fiber reentrainment during
carpet cleaning. For each experiment, three
work-area samples were collected before
and during the carpet cleaning. Figure 2
shows the average airborne asbestos con-
centrations measured before and during
cleaning for each cleaning method and car-
Table 3. Structure Morphology Distribution in Carpet Samples Collected Before and After Carpet
Cleaning
Structure
Type
Chrysotile
Amphibole
Total
Number of
Bundles
1,763
2
1,765
Number of
Clusters
66
0
66
Number of
Fibers
5,893
18
5,911
Number of
Matrices
358
1
359
Total
8,080
21
8,101
5
pet contamination loading. The samples
collected before cleaning were obtained
after the carpet was contaminated to deter-
mine the baseline concentration in the test
room.
The type of cleaning method had no sig-
nificant effect (p=0.58) on the difference
between the airborne asbestos concentra-
tions before and during cleaning. Similarly,
the level of asbestos contamination in the
carpet had no significant effect on fiber
reentrainment (p=0.09). Overall, however,
the mean airborne asbestos concentration
was significantly higher during carpet
cleaning than just before cleaning (p<0.001).
A 95% confidence interval for the mean
airborne asbestos concentration during
carpet cleaning as a proportion of the air-
borne concentration before cleaning showed
that the mean airborne asbestos concentra-
tion was between two and fourtimes greater
during carpet cleaning.
Asbestos fibers in the air during carpet
cleaning activities tended to be smaller in
length than the asbestos fibers remaining in
the carpet after cleaning. Overall, approxi-
mately 17% of the asbestos fibers found in
the carpet were less than 1.0 u,m in length,
whereas approximately 85% of the fibers
observed in the air were greater than 1.0
u,m.
Conclusions
Wet-cleaning significantly reduced the
asbestos concentration in the carpet by
approximately 70%. There was no signifi-
cant change in asbestos concentration after
dry-vacuuming.
Both dry-vacuuming and wet-cleaning of
carpet resulted in a statistically significant
increase in airborne asbestos concentra-
tion. Airborne asbestos concentrations were
increased two to four times during carpet
cleaning. The level of asbestos contamina-
tion in the carpet and the type of cleaning
method used had no significant effect on the
difference between the airborne asbestos
concentration before and during cleaning.
Although these data showed significant in-
creases in airborne asbestos concentra-
tions during cleaning activities in a con-
trolled study under simulated conditions, it
is not known if such increases will occur in
real-world custodial operations. Obviously,
the possibility raises a cause for concern.
Microvacuuming of carpet tended to re-
cover significantly less asbestos than the
bulk-carpet sonic extraction technique. The
mean asbestos recovery from carpet con-
taminated with 1 billion stft2 was 23 million s/
ft2 with microvacuuming and 794 million s/ft2
with sonic extraction. The CV for the
microvacuuming technique (166%) was four
times larger than the CV for the sonic ex-
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Wet Clean Dry Vacuum
Low Contamination
Wet Clean Dry Vacuum
High Contamination
Figure 2. Average airborne asbestos concentrations before and during carpet cleaning.
traction technique (43%). which indicates
that the former technique is less precise.
Recommendations
The removal effectiveness demonstrated
by these two methods is limited to the spe-
cific equipment and work practices used
during this study. Further research should
be conducted to examine the performance
of different HEPA-filtered dry and wet car-
pet cleaners (i.e., performance as a func-
tion of horsepower, static water lift, and
operating air volume and velocity). Further
study also should be conducted to examine
other cleaning methodologies, such as re-
peated carpet cleaning.
This research suggests that normal cus-
todial cleaning of asbestos-contaminated
carpet may result in elevated airborne as-
bestos concentrations. Further research is
needed todetermine actual exposure risk to
custodial workers performing these activi-
ties in buildings containing friable asbestos-
containing materials.
Thefull report was submitted in fulfillment
of Contract No. 68-03-4006, Work Assign-
ment No. 2-10, by PEI Associates, Inc.,
under the sponsorship of the U.S. Environ-
mental Protection Agency.
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John R. Kominsky and Ronald W. Freyberg are with PEI Associates, Inc., Cincinnati,
OH 45246; Jean Chesson is with Chesson Consulting, Washington, DC 20036; and
EricJ. Chatfieldis with Chatfield Technical Consulting Limited, Mississauga, Ontario,
Canada.
William C. Cain and Thomas J. Powers are the EPA Project Officers (see below).
The complete report, entitled "Evaluation of Two Cleaning Methods for Removal of
Asbestos Fibers from Carpet,"(Order No. PB 91-125 740/AS; Cost:
$17.00, subject to change) will be available only from:
National Technical Information Service
5285 Port Royal Road
Springfield, VA 22161
Telephone: 703-487-4650
The EPA Project Officers can be contacted at:
Risk Reduction Engineering Laboratory
U.S. Environmental Protection Agency
Cincinnati, OH 45268
United States
Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati, OH 45268
BULK RATE
POSTAGE & FEES PAID
EPA PERMIT NO. G-35
Official Business
Penalty for Private Use $300
EPA/600/S2-90/053
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