United States
Environmental Protection
Agency
Office of
Toxic Substances
Washington, D.C. 20460
EPA 560/5-89-001
May 1989
Washington, D.C. 20460
Toxic Substances
Guidelines for Conducting
the AHERA TEM Clearance
Test to Determine
Completion of an Asbestos
Abatement Project
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EPA 560/5-89-001
May 1989
FINAL REPORT
GUIDELINES FOR CONDUCTING THE AHERA TEM CLEARANCE TEST
TO DETERMINE COMPLETION OF AN ASBESTOS ABATEMENT PROJECT
Prepared by:
Chesson Consulting
1717 Massachusetts Ave.,NW
Suite 601
Washington, DC 20036
Battelle
Arlington Office
2101 Wilson Boulevard
Arlington, VA 22201
Contract No. 68-02-4294
for the:
Design and Development Branch
Exposure Evaluation Division
Office of Toxic Substances
Office of Pesticides and Toxic Substances
U.S. Environmental Protection Agency
Washington, DC 20460
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This document has been reviewed and approved for publication by
the Office of Toxic Substances, Office of Pesticides and Toxic
Substances, U.S. Environmental Protection Agency. The use of
trade names or commercial products does not constitute Agency
endorsement or recommendation for use.
ii
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AUTHORS AND CONTRIBUTORS
This document was prepared under contract to the U.S.
Environmental Protection Agency. The primary author was Jean
Chesson of Chesson Consulting. Barbara Leczynski, Ted Berner,
and Toni Hudson of Battelle were responsible for contract
administration and coordinated document production. Bradley
Schultz (Task Manager), Mary Frankenberry (Project Officer),
Cindy Stroup, Betsy Dutrow, Joe Breen, and Edie Sterrett of EPA's
Exposure Evaluation Division participated in early discussions
and subsequent reviews and revisions.
ACKNOWLEDGMENTS
We acknowledge EPA's Hazard Abatement Assistance Branch for their
support of this project and reviews of the draft manuscript.
Their comments and those from the peer review panel improved the
document. Amy Doll of Chesson Consulting prepared the numerical
examples. The cover was designed by Mark Von Bernewitz-Wright.
111
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SUMMARY
Asbestos abatement carried out in schools is subject to
regulations under the Asbestos Hazard Emergency Response Act of
1986 (AHERA). The AHERA rule (40 CFR Part 763) includes
procedures for determining when an asbestos abatement site is
sufficiently clean for the containment barriers to be removed.
After the abatement site has been subject to a thorough visual
inspection, air samples are collected. In most cases, the
samples must be analyzed by transmission electron microscopy
(TEM) .
This document provides guidance for conducting the TEM clearance
test with emphasis on interpretation of the results. The three
components of the test the Initial Screening Test, the Blank
Contamination Test, and the Z-test are described and
illustrated with numerical examples.
iv
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1. INTRODUCTION
As required under the Asbestos Hazard Emergency Response Act of
1986 (AHERA), EPA has promulgated a rule regarding inspections,
abatement, and management of asbestos-containing material in
schools (40 CFR Part 763). The rule includes procedures for
determining when an asbestos abatement site is sufficiently clean
for the containment barriers to be removed. After the abatement
site has been subject to a thorough visual inspection, air
samples are collected. In most cases, the samples must be
analyzed by transmission electron microscopy (TEM).
This document provides guidance for conducting the TEM clearance
test with emphasis on interpretation of the results. The
guidance is intended for abatement project monitors, industrial
hygienists, asbestos consultants and others who are responsible
for interpreting air sampling data. Details on sampling and
analytical protocols are not included. Readers should refer to
the AHERA rule for details on these topics and to determine the
circumstances under which alternative clearance procedures may be
used. Readers are also urged to consult the latest version of
the AHERA rule for revisions that may have been made since the
publication of this document.
2. BACKGROUND
The AHERA TEM clearance test is based on a comparison of airborne
asbestos levels inside the work site with those outside the work
site. This approach was adopted since an abatement contractor
could not be expected to achieve airborne asbestos concentrations
inside the work site lower than those of the incoming air.
"Outside" does not necessarily mean outdoors. When air intake to
the work site is from other parts of the building rather than
from outdoors, indoor samples may be collected as the basis for
comparison. However, outdoor samples are recommended in most
circumstances because they are unlikely to be affected by poor
work practices that might contaminate areas outside the work
site.
Airborne asbestos measurements are subject to variation due to
variability of the distribution of asbestos in the air and
variability introduced by the sampling and analytical procedures.
The clearance test must account for both sources of variation in
order to achieve a high probability of correct clearance
decisions. Therefore the test requires a minimum of five samples
collected inside the work site and five samples collected outside
the work site, and uses a statistical test, the Z-test, to
determine if inside levels are statistically higher than outside
levels. The Z-test differs slightly from the t-test recommended
in previous EPA guidance documents (USEPA 1985a, 1985b) by fixing
the amount of variability associated with the measurements rather
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than estimating it from the data. Consequently, the Z-test is
simpler to calculate.
The Z-test is preceded by two preliminary tests, an initial
screening test and a blank contamination test. The initial
screening test is intended to reduce the cost of analysis when
the concentration of asbestos structures on sample filters
collected inside the work site is comparable to the concentration
typically observed on blank filters (filters through which no air
has been drawn). Asbestos structures on blank filters may be the
result of contamination during filter manufacture, for example.
If the concentration on filters used to sample inside the work
site is comparable to typical blank contamination levels, the
work site passes the clearance test without requiring analysis of
the outside samples. The initial screening test is based on the
concentration per area of filter, not concentration per volume of
air, because it considers asbestos structures from sources other
than the sampled air. Filter concentrations less than or equal
to 70 s/mm2 are considered indistinguishable from blank
contamination levels. A measurement within this range suggests
that few, if any, asbestos structures have been contributed by
the sampled air.
If the average filter concentration for the inside samples is
greater than 70 s/mm2, a minimum of three blanks are checked to
insure that the particular filter lot used was not contaminated
beyond typical levels. Like the initial screening test, the
blank contamination test is based on structures per area of
filter because it involves asbestos structures from sources other
than the sampled air.
Together, the three tests (the initial screening test, the blank
contamination test, and the Z-test) make up the AHERA TEM
clearance test.
3. SAMPLING
Sampling must be performed by a qualified individual who is
completely independent of the abatement contractor. Although the
AHERA rule does not impose specific requirements, it is suggested
that the person should be professionally licensed and/or have
received relevant training.
Since circumstances vary among abatement sites, professional
judgment is needed to ensure that the samples accurately
represent airborne asbestos levels inside and outside the work
site. This section provides guidance on the number and location
of samples. Refer to Section III B of the AHERA rule and USEPA
(1985b) for further details on the sampling protocol.
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of Samples
The clearance test requires a minimum of five samples inside the
work site, five samples outside the work site, and three blanks.
Additional samples will improve the performance of the clearance
test (i.e., increase the probability of making a correct
clearance decision). Additional samples are recommended for
large or complex work sites that consist of several rooms or
distinct areas. Provided the minimum requirements are met, it is
not necessary to have an equal number of samples inside and
outside the work site.
For example, if the work site consists of eight adjacent rooms,
the local educational authority (LEA) may choose to collect a
sample in each of the eight rooms and five samples outside the
work site. The additional three samples inside the work site
improve the performance of the clearance test and also provide
extra assurance that each room has been adequately cleaned. If
the work site fails the clearance test, the additional samples
may help isolate the problem to one or more rooms and indicate
where cleaning efforts should be concentrated. Note, however,
that the entire work site must be resampled, not just the room or
area in which high concentrations were measured during the
original test.
The desirability of exceeding the minimum requirements,
especially for large or complex abatement projects, should be
considered when the abatement project is being planned.
Specifications for sampling and interpretation of results should
be clearly stated in the contract between the LEA and the
abatement contractor.
The clearance test must be based on all samples analyzed. It is
not permissible to analyze more than the minimum number of
samples then choose the "best" results for inclusion in the
calculations. It is acceptable, however, to analyze a subset of
the samples collected, provided the subset of samples is selected
at random without knowledge of the concentration of asbestos
structures on the filters.
For example, a school district may set up 6 samplers in the work
site to insure against the possibility of a lost or damaged
sample. At the laboratory, 5 samples are selected at random from
the 6 provided. If a sample is unsuitable for analysis, or is
accidentally destroyed, the remaining sample is analyzed and the
minimum of 5 samples is still achieved. If all samples are
suitable for analysis and the school district decides to analyze
all 6, then the results of the 6 analyses must be included in the
clearance test calculations.
The AHERA rule does not explicitly address the case of samples
that are so overloaded with material (asbestos or otherwise) that
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they cannot be analyzed by the laboratory. In most cases, an
overloaded sample is indicative of a dirty work site that needs
recleaning.
Inside the Work Site
Samplers should be located to provide a representative sample of
air within the work site. If the work site is a single room,
locate the samplers throughout the area. If the work site
consists of several rooms, place a sampler in each room, or in a
representative subset of rooms. Random numbers may be used to
select a representative subset. Each sampler should be placed so
that it is subject to normal air circulation. Avoid room
corners, obstructed locations, and sites near windows, doors, or
vents. Ensure that the sampler is not sampling exhaust fumes
from the pump. Oil droplets on the filter can adversely affect
the analysis.
Outside the Work Site
Samples should be representative of air entering the work site.
Place samplers so that they do not sample any air that may escape
from the work site. Recommended distances are at least 50 feet
from the entrance to the work site and at least 25 feet from the
containment barriers. If any potential sources of fiber release
(e.g., tears in the containment barrier, spillage of asbestos
waste) are identified while the abatement work is in progress,
these locations should be avoided when selecting the outside
sampling locations.
Taking makeup air from outside the building, or passing makeup
air through a HEPA filtration system before it enters the work
site eliminates the need to use indoor samples taken outside the
work site as the basis for comparison. The contractor no longer
has to contend with other sources of airborne asbestos and should
be able to clean the work site to levels comparable with
outdoors. Sampling outdoors is recommended because it reduces
the likelihood of the contractor improperly passing the clearance
test due to poor work practices that increase airborne asbestos
levels outside the work site.
Outdoor samplers should be placed at least 3 feet apart,
preferably at ground level rather than on a roof. Protect the
samplers from adverse weather and avoid obstructions that may
influence wind patterns. If a roof-top site is necessary, avoid
locations near vents or other structures.
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3 3 S*ffllfl
The AHERA rule specifies a minimum air volume of 560 liters for
25 mm diameter filters and 1,250 liters for 37 mm diameter
filters. Recommended ranges are 1,200 liters to 1,800 liters and
2,800 liters to 4,000 liters respectively. Note that the initial
screening test cannot be used when the volume of air is below the
recommended range. Lower volumes require TEM analysis of a
larger area of filter in order to achieve the required analytical
sensitivity. This is discussed further in the next section.
4. LABORATORY ANALYSIS
Air samples are analyzed by TEM according to the protocol
specified in the rule. The rule allows flexibility in the choice
of volume of air sampled and the amount of filter examined,
provided the analytical sensitivity (the concentration
represented by a single fiber) is no greater than 0.005
structures per cubic centimeter of air (s/cc) . To maintain the
analytical sensitivity at 0.005 or less, a small volume of air
must be compensated for by examining a larger area of the filter.
Conversely, examination of a small area of the filter must be
compensated for by collecting a larger volume of air.
A laboratory accreditation program for TEH analysis is being
established by the National Institute of Standards and Technology
(NIST, formerly the National Bureau of Standards) . Only
accredited laboratories will be permitted to analyze samples for
compliance with AHERA. Until the accreditation program is
operational, LEAs must use laboratories which follow the protocol
stated in Appendix A of the rule.
5. INTERPRETATION OF RESULTS
Figure 1 shows each step in the clearance test. The initial
screening test is performed first. If the inside samples pass
the initial screening test, the work site passes and no further
analysis is required. If the inside samples do not pass the
initial screening test, the blanks are examined. If the blanks
fail the blank contamination test, the source of contamination
must be identified and corrected, and new samples collected. If
the blanks pass the blank contamination test, the Z-test is
performed to determine whether the work site passes or fails the
clearance test.
The following sections describe how to perform the initial
screening test, the blank contamination test, and the Z-test.
The numerical examples are hypothetical and represent only a
subset of the possible outcomes and decisions.
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Perform Initial
Screening Test
Figure 1. The AHERA TEM clearance test.
6
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5.1 Initial Screening Test
The laboratory should report the asbestos structure concentration
per square millimeter of filter (s/mm2) for each inside sample.
Calculate the arithmetic mean (average) of all the inside
samples. If the arithmetic mean is less than or equal to 70
s/mm2, the inside samples pass the initial screening test and the
work site passes the clearance test.
In the three examples below it is assumed that the minimum volume
requirements for the initial screening test have been met. When
this is not the case, the analysis proceeds directly to the blank
contamination test.
Example 1. In this example the LEA decided to collect and
analyze 8 inside samples. The results are shown in Figure 2.
The arithmetic mean is less than 70 s/mm2 and therefore the
samples pass the initial screening test. Note that zeros are
included in the calculation of the arithmetic mean. The work
site passes the clearance test and no further analyses are
required.
Example 2. The results of analysis of 5 inside samples are shown
in Figure 3. The arithmetic mean is greater than 70 s/mm and
therefore the samples do not pass the initial screening test.
The LEA gives the abatement contractor the option of recleaning
immediately or carrying on with the blank contamination test and
Z-test. The abatement contractor is convinced that the work site
has been thoroughly cleaned and opts for continuing with the
test.
Example 3. Five inside samples give the concentrations shown in
Figure 4. The arithmetic mean is less than 70 s/mm2 and
therefore the samples pass the initial screening test. The
result of the fourth analysis, however, appears to be unusually
high compared with the other values. The LEA decides as a
precautionary measure to ask the abatement contractor to reclean
the room where the fourth sample was collected. Although this
eventuality was not covered in the original contract and no
action is required under the AHERA rule, the LEA decides that the
additional expense is justified. (Note that there is a great
deal of uncertainty associated with a single estimated
concentration. That is why the clearance test requires multiple
samples. Therefore caution should be used in interpreting
individual values.)
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INITIAL SCREENING TEST
Work Sheet
Inside Samples
f inside samples, nlf = 8
Sample 1
Sample 2
Sample 3
Sample 4
Sample 5
Sample 6
Sample 7
Sample 8
35.80 s/mm2
0.00 s/mm2
17.90 s/mm2
0.00 s/mm2
17.90 s/mm2
0.00 s/mm
17.60 s/mm2
35.90 s/mm2
Sample PI s/mnv
Total 125.10
Mean = Total/n, = 125.10 / 8
= 15.64
Result
Figure 2. The Initial Screening Test Example 1. In this
example the work site passes and no further analyses are
required.
8
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INITIAL SCREENING TEST
Work Sheet
Inside Samples
# inside samples, rt|, = 5
Sample 1 71.60 s/mm2
Sample 2 107.40 s/mm2
Sample 3 89.50 s/mm2
Sample 4 53.70 s/mm2
Sample 5 89.50 s/mm2
Sample 6 s/mm2
Sample 7 s/mm2
Sample 8 s/mm2
Sample n, s/mm2
Total 411.70
Mean = Total/n, = 411.70 / 5
= 82.34
Result
Figure 3. The Initial Screening Test Example 2. In this
example the work site fails. The abatement contractor,
convinced that the site is clean, opts to continue with the
blank contamination and Z-tests.
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INITIAL SCREENING TEST
Work Sheet
Inside Samples
# Inside samples, hi. * 5
Sample I 3S.80 $/m?
Sample 2 53.70 s/mro2
Sample 3 0.00 s/mm2
Sample 4 23?.70 s/mm2
Sample 5 17.90 s/mm2
Sample 6 s/mm2
Sample 7 .,,,,. . s/mm2
Sample 8 s/nm?
Sample tij s/mm2
Total 340.10
Mean = TotaT/n, = 340.10 / 5u
* 68.02
Result
Figure 4. The Initial Screening Test Example 3. In this
example the work site passes and no further analyses are
required under the AHERA rule. However, as a precautionary
measure, the LEA decides to reclean the room where sample 4
was collected.
10
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5.2 Blank Contamination Test
The results of the analyses of the three blanks are reported as
structures per square millimeter of filter. Calculate the
arithmetic mean of the three values. If the arithmetic mean is
less than or equal to 70 s/mm, the blanks pass the blank
contamination test and one may proceed to the Z-test. If the
arithmetic mean is greater than 70 s/mm2, it is likely that the
blanks have been contaminated by asbestos structures from a
source other than the sampled air. The validity of the inside
and outside samples is questionable. They must be discarded'and
new samples collected.
Before collecting new samples, attempt to identify and eliminate
the source of contamination. If asbestos structures are present
on the sealed blank, the filters may have been contaminated
during manufacture. Select new filters from lots that have been
prescreened. (Laboratories are required to screen filters from
the lots they use for their internal quality control.) If the
majority of asbestos structures are on the field blanks,
contamination may have occurred during the field sampling or
laboratory analysis. Check field procedures and ask the
laboratory for the results of blank analyses that they are
required to perform as a part of their laboratory quality control
program. During the resampling ensure that the sampling,
handling, and analysis protocols are strictly followed to avoid a
repeat of the contamination problem.
Example 4. Analysis of three blanks gives the results shown in
Figure 5. The arithmetic mean of the three concentrations is
less than 70 s/mm and the blanks pass the contamination test.
The laboratory proceeds with the analysis of the outside samples.
Example 5. The three blanks in Figure 6 do not pass the blank
contamination test. The cause of the failure appears to be the
field blank collected inside the work site. The sampling
technician recalls that the sampling cassettes were accidentally
stored in the work site while the abatement was in progress. A
new supply of cassettes is obtained and the entire sampling and
analysis procedure is repeated.
11
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BLANK CONTAMINATION TEST
Work Sheet
Blanks
# blanks, nB, = 3
0.00 s/itro2
7.60 s/mm2
Blank nB
s/mro2
s/mm2
s/nro2
Mean * Tota1/nB = 17.60 / 3
a S.87
Result
Mean & 70
MM
PASS
Mean > 70
FAIL
Figure 5. The Blank Contamination Test Example 4. In
this example the blanks pass the test and the laboratory
proceeds to the analysis of the outside samples.
12
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BLANK CONTAMINATION TEST
Work Sheet
Blanks
# blanks, nB, * 3
Blank nB s/mrn2
Total Z47.80
Mean = TotaVnB = 247.80 73
a 82.60
Result
Figure 6. The Blank Contamination Test Example 5. In
this example the blanks fail the test. The problem must be
corrected and a new set of samples (inside, blank, and
outside) collected.
13
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5 . 3 2- test
After passing the blank contamination test, the outside samples
are analyzed and compared with the inside samples using the Z-
test. Note that the Z-test is a comparison of airborne asbestos
levels inside and outside the work site and therefore is based on
the concentrations per cubic centimeter of air.
The Z-test uses natural logarithms. Since it is not possible to
take the logarithm of zero, samples on which no asbestos
structures were detected are given a small positive value. In
the AHERA rule this small value is referred to as the "detection
limit," although this term is used differently in other contexts.
The statement is meant to apply only to the Z-test, not to the
initial screening test. In its current form, the wording of the
rule is ambiguous. (A clarification is anticipated in an
upcoming revision.) In line with the expected revision, it is
recommended that 0.0025 s/cc be substituted for any zero
concentration prior to taking logarithms. Calculate the _
arithmetic mean of the logarithms for the inside samples (Yj)
and the arithmetic mean of the logarithms for outside samples
(Y0) . Then calculate Z according to the formula
Z =
0.8
where n} is the number of inside samples and n0 is the number of
outside samples. If Z is less than or equal to 1.65, the inside
and outside concentrations are not statistically different from
each other and the work site passes the clearance test. If Z is
greater than 1.65 the work site fails the clearance test. The
work site must be recleaned and the sampling and analysis
procedures repeated.
Example 6. Figure 7 shows the structure concentrations per cubic
centimeter of air for five inside samples and five outside
samples. No structures were observed on two of the outside
samples. Their concentrations were replaced by 0.0025 before
taking logarithms. Z is less than 1.65 and therefore the work
site passes the clearance test.
Example 7. In this example the LEA decided to collect and
analyze 8 inside samples (one per room) and 5 outside samples.
The results are shown in Figure 8. Z is greater than 1.65 and
the work site failed the clearance test. The entire work site
was recleaned with special emphasis given to the two rooms in
which the fifth and seventh samples were collected.
14
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Z-TEST
Work Sheet
Inside Samples
# inside samples, P|, = 5
s/cc 1n(s/cc)
Sample 1 0.0022 S/cc -6.1193
Sample 2 0.0071 s/cc -4.9477
Sample 3 0.0115 s/cc -4.4654
Sample 4 0.0045 s/cc -S.4037
Sample 5 0.0057 s/CC -5.1673
Sample 6 ^_^__ s/cc , .
Sample 7 s/cc
Sample 8 s/cc
Sample
s/cc
Total -26.1034
Y, = Total/n, = -26.1034 / 5
= -5.2207
Z =
- Y
0.8 (1/ni + l/n0)
1/2
Outside Samples
# outside samples, PQ, = 5_
s/cc ln(s/cc) .'
Sample 1 0.0031 s/cc -5.7764
Sample 2 0.0085 s/cc -4.7677,
Sample 3 0 - 0.0025 s/cc -5.9915
Sample 4 0.0072 s/cc -4.9337
Sample 5 0 - 0.0025 s/cc -5.9915
Sample 6 s/cc ..
Sample 7 s/cc ^
Sample 8 s/cc
Sample
s/cc
Total -27.4606
Y0 = Total/n0 = -27.4606 / 5
= -5.4921
-5.2207 - -5.4921
0.8 (1/5. + l/5_)w
Result
0.537
Z < 1.65 I Z > 1,65
*"«
PASS
Figure 7. The Z-test Example 6. In this example the
work site passes the clearance test.
15
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Z-TEST
Work Sheet
Inside Samples
# inside samples,
ln(s/cc)
-4.6777
-4.9477
-4.4654
-5.4037
-3.1749
-4.8036
-3.7091
-4.7677
Sample
s/cc
Total -35.9498
Y, * Total/nj ~ -35.9498 / 8
s -4.4937
Z =
0.8 (1/ni + I/no)1
Outside Samples
# outside samples, n0, = S
s/cc ln(s/cc)
Sample 1 0.0065 s/cc -5.0360
Sample 2 0.0070 s/cc -4.9618
Sample 3 0.0053 s/cc -5.2400
Sample 4 0.0035 s/cc -S.65SO
Sample 5 0.0043 s/cc -5.4491
Sample 6 s/cc
Sample 7 s/cc
S/CC -
Sample 8
Sample no
s/cc
Total -26.3419
Y0 = Total/no = -26.3419 /_5_
= -5.2684
-4.4937 - -5.2684
0.8
Result
1.699
Figure 8. The Z-test Example 7. In this example the
work site fails the clearance test. The site must be
recleaned and a new set of samples collected.
16
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Example 8. The results shown in Figure 9 give a value of Z that
is less than 1.65 and therefore the work site passes the test.
However, airborne asbestos levels both inside and outside the
work site were somewhat higher than those measured after
abatement projects in neighboring schools. The LEA decided that
it would be prudent to investigate the matter further and asked
its asbestos consultant to investigate and report on other
potential sources of asbestos both inside and outside the
building. Meanwhile, a special asbestos operations and
maintenance program remained in effect throughout the school.
Example 9. The Z-value in this example is greater than 1.65
(Figure 10). Therefore the work site does not pass the clearance
test. Examination of the laboratory report revealed that the
asbestos structures identified on the inside samples were
amosite, while the removal had involved only chrysotile asbestos.
After a thorough inspection, previously undetected amosite
insulation was discovered on pipes above the suspended ceiling.
Minor damage to the pipe insulation was repaired and the work
site, including above the ceiling, was recleaned before
collecting a new set of air samples.
The preceding examples, as well as demonstrating how to perform
the Z-test, indicate that the LEA can and should take into
account additional information to decide when an abatement
project is complete. Where possible, the contract with the
abatement contractor should reflect this to avoid later
disagreements. The laboratory report will indicate the type of
asbestos (for example, chrysotile or amphibole) and the types of
asbestos structures observed (individual fibers or complex
structures such as bundles, clusters, or matrices consisting of
multiple fibers). The LEA might consider recleaning, if, for
example, the work site just passes the Z-test but the inside
samples are predominantly amphibole, whereas the outside are
exclusively chrysotile. A predominance of complex structures
inside the work site compared to single fibers outside the work
site, may also suggest that conditions inside the work site are
not yet comparable with those outside the work site.
17
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Z-TEST
Work Sheet
Inside Samples Outside Samples
# inside samples, nj, * ,,,&,, t outside samples, no> = ,,,,.8,
s/cc ln(s/cc) s/cc 1n(s/cc)
Sample 1 0.0093 s/cc -4.6777 Sample I 0.0065 s/cc -5.0360
Sample 2 0.0154 s/cc -4.1734
Sample 3 0.0115 s/cc -4.4654
Sample 4 0.0245, s/cc -3.7091
Sample 5 0.0418 s/cc -3.1749
Sample 6 0.0098 s/cc -4.6254
Sample 7 0.0162 S/cc -4.1227
Sample 8 0.0326 s/cc -3.4234
Sample nj s/cc
Total -32.3720
Yt « Total/n, s -32.3720 / 8
» -4.0465
Z = YI ' Yo
0.8 (1/n, + l/n0)w
1 Z £ 1.65
1 I^PASS^
Sample 2 0.0154 s/cc -4.1734
Sample 3 0.0341 S/CC -3.3785
Sample 4 0.0287 s/cc -3.5509
Sample 5 0.0043 s/cc -5.4491
Sample 6 0.0136 s/cc -4.2977
Sample 7 0.0057 S/cC -5.1673
Sample 8 0.0223 s/cc -3.8032
Sample rv-v s/cc
Total -34.8559
Yo * Total/no * -34.8559 / 8
* -4.3570
-4.0465 - -4.3570 = Qm
0.8 (l/8_ + l/R_)m
Re$ult
Z > 1.6$ ||
**J
XJ FAIL 1
Figure 9. The Z-test Example 8. In this example the
work site passes the clearance test.
18
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Z-TEST
Work Sheet
Inside Samples
# inside samples, nj, =
.s/cc
Sample 1 0.0071 s/cc
Sample 2 0.0204 s/cc
Sample 3 0.0079 s/cc
Sample 4 0.0150 s/cc
Sample 5 0.0095 s/cc
Sample 6 _ s/cc
Sample 7 _ s/cc
Sample 8 _ __ s/cc
1n(s/cc)
-4.9477
-3.8922
-4.8409
-4.1997
-4.6565
Sample nr
s/cc
Total -22.5370
= Total/n, = -22.5370 /_5_
= -4.5074
Z =
Y, - Yr
0.8 (1/n, + l/n0)
ira
Outside Samples
I outside samples, HQ, = 5
s/cc 1n(s/cc)
Sample 1 0.0065 s/cc -5.0360
Sample 2 0.0037 s/cc -5.5994
Sample 3 0.0050 s/cc -5.2983
Sample 4 0.0028 S/cc -5.8781
Sample 5 0.0043 s/cc* -5.4491
Sample 6 s/cc
Sample 7 s/cc
Sample 8 ^^___ s/cc ,
Sample no
s/cc
Total -27.2609
Y0 = Total/n0 = -27.2609 / 5
= -5.4522
-4.5074 - -5.4522
0.8
Result
1.867
Figure 10. The Z-test Example 9. In this example the
work site fails the clearance test. The site must be
recleaned and new samples collected.
19
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REFERENCES
USEPA. 1985a. U.S. Environmental Protection Agency. Guidance for
controlling asbestos-containing materials in buildings.
Washington, DC: Office of Toxic Substances, USEPA. EPA 560/5-85-
019.
USEPA. 1985b. U.S. Environmental Protection Agency. Measuring
airborne asbestos following an abatement action. Research
Triangle Park, NC: Environmental Monitoring Systems Laboratory
and Office of Toxic Substances, USEPA. EPA 600/4-85-049.
20
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APPENDIX A
WORK SHEETS
Note: Identifying information such as location, sample
ID, date, and signature of the evaluator should be
added if the work sheets are to be used as permanent
documentation.
21
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INITIAL SCREENING TEST
WORK SHEET
Inside Samples
# inside samples, HI, =
Sample 1
Sample 2
Sample 3
Sample 4
Sample 5
Sample 6
Sample 7
Sample 8
Sample n,
Total
s/mm2
s/mm2
s/mm2
s/mm2
s/mm2
s/mm2
s/mm2
s/mm2
s/mm2
Mean = Total/ni » /_
Circle Result
Mean < 70
PASS
Mean > 70
FAIL
22
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BLANK CONTAMINATION TEST
WORK SHEET
B1anks
# blanks, nB, =
Blank 1
Blank 2
Blank 3
Blank 4
Blank 5
Blank 6
Blank 7
Blank 8
Blank ns
Total
s/mm2
s/nrni2
s/mm2
s/mm2
s/mm2
s/mm2
s/mm2
s/mm2
*
s/mm2
Mean = Total/nB = /_
Circle Result
Mean < 70
PASS
Mean > 70
FAIL
23
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Z-TEST
WORK SHEET
Inside Samples
# Inside samples, n,,
s/cc
Y, = Total/n, =
ln(s/cc)
Sample 1
Sample 2
Sample 3
Sample 4
Sample 5
Sample 6
Sample 7
Sample 8
Sample n,
s/cc
s/cc
s/cc
s/cc
s/cc
s/cc
s/cc
s/cc
*
s/cc
Total
Outside Samples
# outside samples, n0, -
s/cc In(s/cc)
Sample 1
Sample 2
Sample 3
Sample 4
Sample 5
Sample 6
Sample 7
Sample 8
*
Sample r\n
Y0 = Total/n0 =
s/cc
s/cc
s/cc
s/cc
s/cc
s/cc
s/cc
s/cc
s/cc
Total
/
Y, - Ye
0.8 (1/n, + l/n0)
1/2
0.8
Circle Result
kV2
Z <, 1.65
PASS
Z > 1.65
FAIL
24
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REPORT DOCUMENTATION
PAGE
1. REPORT NO.
" EPA 560/5-89-001
3. Recipient's Accession No.
4. Title and Subtitle
Guidelines for Conducting the AHERA TEM Clearance Test to Determine
Completion of an Asbestos Abatement Project
5. Report Date
May, 1989
7. Authors)
Chesson, J.
8. P«rforming Organization Rapt. No.
9. Performing Organization Name and Address
Chesson Consulting, 1717 Massachusetts Ave, NW, Washington, DC 20036
Battelle, Arlington Office, 2101 Wilson Boulevard, Arlington, VA 22201
10. ProJect/Task/Work Unit No.
11. Contract(C) or Grant(G) No.
(o 68-02-4294
(C)
12. Sponsoring Organization Nam* and Addrass
U.S. Environmental Protection Agency
Office of Toxic Substances
Exposure Evaluation Division (TS-798)
401 M Street, SW, Washington, DC 20460
13. Type of Raport & Pariod Covarad
Peer-reviewed report
14.
IS. Supplamantary Notas
1C. Abstract (Umit: 200 words)
Guidance is provided for conducting the transmission electron microscopy clearance test required under the
Asbestos Hazard Emergency Response Act (40 CFR Part 763) to determine when an asbestos abatement site is
sufficiently clean for the containment barriers to be removed. Emphasis is on interpretation of the results.
The three components of the clearance test - the initial screening test, the blank contamination test, and the
Z^test - are described and illustrated with numerical examples.
7. Dominant Analysis .. Descriptors
AHERA, asbestos, asbestos air monitoring, asbestos abatement, clearance, TEM, transmission electron
microscopy.
b. Identlflera/Open-Ended Terms
e. COSATI Flald/Qreup
Availability Statement
It. Security Class (This Report)
Unclassified
20. Security Class (This Page)
Unclassified
21. No. of Pe«es
29
a. Price
(MeANSI-ZM.li)
See Instructions on Reverse
OPTIONAL FORM 272 (4-77)
(Formerly NTIS-35)
Department of Commerce
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