United States
Environmental Protection
Agency
Solid Waste and
Emergency Response
EPA 540-R-97-028
OSWER 9240.1-33
PB97-963503
xvEPA
Superfund
SUPERFUND METHOD FOR THE
DETERMINATION OF* RELEASABLE
ASBESTOS IN SOILS AND
BULK MATERIALS
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SUPERFUND METHOD FOR THE
DETERMINATION OF RELEASABLE
ASBESTOS IN SOILS
AND BULK MATERIALS
INTERIM VERSION
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DISCLAIMER
Although this work was completed under contract to the U.S. Environmental Protection Agency,
such support does not signify that the work or the conclusions drawn from the work necessarily
reflect the views and policies of the Agency, nor does the mention of trade or commercial
products constitute endorsement or recommendation for use.
A series of conceptual design figures are included in this method to assist users with their own
design and construction of an appropriate dust generator for supporting this method. However,
these figures are not to be construed as formal construction drawings and IGF Technology will
accept no liability for their reference or use.
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TABLE OF CONTENTS
1.0 INTRODUCTION . . . . : ....... . ... . 1-1
r '.-,'' .
2.0 BACKGROUND . .2-1
2.1 REQUIREMENTS FOR A METHOD DESIGNED TO SUPPORT RISK
ASSESSMENT ........... . . 2-1
2.1.1 Sensitivity . . 2-2
2.1.2 Precision ..:..../. 2-2
2.1.3 Asbestos Characteristics 2-3
2.1.4 Reporting Requirements .'... 2-4
2-2 ASBESTOS CONTAINING MATERIALS TYPICALLY ENCOUNTERED
AT SUPERFUND SITES .. .. ', . 2-5
2.3 REQUIREMENTS FOR FACILITATING REPRODUCIBILITY BETWEEN
LABORATORIES.. ......... ..~ . . 2-6-
2.4 COST CONSIDERATIONS . .......... . . . . 2-7
3.0 OVERVIEW OF METHOD ..'.,.'. . . . ., . ..:..... 3-1
4.0 DEFINITIONS . .; . . . . . . , . . . 4-1
5.0 SYMBOLS AND ABBREVIATIONS . . . 5-1
5.1 SYMBOLS . . 5-1
5.2 ABBREVIATIONS............ 5-4
6.0 FACILITIES AND EQUIPMENT .6-1
6.1 SAMPLE COLLECTION EQUIPMENT AND CONSUMABLE SUPPLIES .... 6-1
6.2 LABORATORY FACILITIES .........:...,... 6-2
6.3 THE DUST GENERATOR AND APPURTENANT EQUIPMENT .......... 6-2
6.4 SPECIMEN PREPARATION EQUIPMENT . . . . : 6-3
6.5 OTHER LABORATORY EQUIPMENT . . 6-3
6.6 CONSUMABLE/REUSABLE LABORATORY SUPPLIES 6-3
7.6 REAGENTS ............. ...... 7-1-
8.0 SOIL OR BULK SAMPLE COLLECTION ............;.. 8-1
8.1s SAMPLE COLLECTION . . : 8-1
8.1:1 Sampling to Derive Estimates of Asbestos Concentrations in
a Road Surface ; . ... 8-2
8.1.2 Sampling a Mine Tailings Pile to Derive Estimates of
Asbestos Concentrations Within the Pile . 8-2
8.2 FIELD PREPARATION . . . . . ...:... . 8-3
8.2.1 Weighing ; . :. 8-3
8.2.2 Size Reduction .^ .. 8-5
8.2.3 Sample Homogenization and Splitting ............. 8-5
, ,8.3 COMPOSITING SAMPLES (OPTIONAL) . : . . . 8-15
8.4 SAMPLE HANDLING AND SHIPMENT ...... 8-16
in
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TABLE OF CONTENTS (cont)
9.0 SAMPLE PREPARATION BY DUST GENERATION . 9-1
9.1 SAMPLE RECEIVING AND STORAGE 9-1
9.2 SAMPLE HOMOGENIZATION AND SPLITTING IN THE LABORATORY 9-2
9.3 DUST GENERATOR SETUP :..'.'.'. 9-2
9.3.1 Conditioning a Stock of Filters 9-2
9.3.2 Initiating Humidity Control ''....'. . ... 9-3
9.3.3 Priming the Scrubber 9.3
9.3.4 Adjusting Initial Air Flow 9-3
9.4 DUST GENERATOR OPERATION ....'.'.'.'.'.'.'.'.'.'. 9-6
9.4.1 Loading the Tumbler 9-6
9.4.2 Conditioning the Sample. 9.7
9.4.3 Initiating a Run '. 9.7
9.4.4 Monitoring the Rate of Respirable Dust Generation 9-8
9.4.5 Generating Appropriately Loaded Filters for Asbestos
Analysis . 9.9
9.4.6 Obtaining Asbestos Samples from the Scrubber ....... 9-11
9.5 CLEANING THE DUST GENERATOR 9-12
10.0 PREPARATION OF SPECIMEN GRIDS FOR TEM ANALYSIS 10-1
10.1 PREPARATION OF SPECIMEN GRIDS FROM FILTERED ALIQUOTS
OF THE SCRUBBER SUSPENSION 10-1
10.2 SPECIMEN GRID PREPARATION FROM FILTERS COLLECTED OVER
THE 1ST OPENING OF THE ELUTRIATOR . 10-1
10.2.1 Specimen Grid Preparation Using a Direct Transfer
Technique . 10-2
10.3 Specjmen Grid Preparation Using an Indirect Transfer Technique 10-2
11.0 PROCEDURES FOR.ASBESTOS AND DUST ANALYSIS 11-1
11.1 PROCEDURES FOR ASBESTOS ANALYSIS '.','. H-1
11.1.1 Analysis of Specimen Grids Prepared from Filters Collected
Over the 1ST Opening of the Elutriator 11-1
11.1.2 . Analysis of Specimen Grids Prepared from Filtered Scrubber
Suspension , 11.3
11.2 EVALUATING THE RATE OF RELEASE OF RESPIRABLE DUST " 11-5
11.3 DETERMINING THE CONTENT OF RESPIRABLE DUST .... 11-8
11.4 DETERMINING THE CONTENT OF ASBESTOS 11 -10
11.4.1 Based on Directly Prepared Filters Collected Over the 1ST
Opening of the Elutriator 11-10
11.4.2 Based on Specimens Prepared from Scrubber Water 11-12
11.4.3 Procedure for Adjusting Asbestos Concentrations to
Account for the Presence of Coarse Material in the Sampled
Matrix . 11-13
12.0 PERFORMANCE CHARACTERISTICS AND QUALITY CONTROL/QUALITY
ASSURANCE REQUIREMENTS 12-1
12.1 METHOD PERFORMANCE ....'. "
IV
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TABLE OF CONTENTS (cont)
12.2
12.1.1 Analytical Sensitivity : 12-1
12.1.2 Precision 12-1
12,1.3 Accuracy 12-2
12.1.4 Asbestos Characteristics . ...... 12-3
12.1.5 Reporting Requirements .... 12-3
QUALITY CONTROL REQUIREMENTS . 12-3
12.2.1 Blanks ..'..-. ....;.....;.... 12-3
12.2.2 Duplicates/Replicates , ................. 12-5
13.0 REPORTING REQUIREMENTS . , . . 13-1
13.1 FIELD AND LABORATORY NOTEBOOKS 13-1
13.1.1 Field Notebooks ..13-1
13.1.2 Laboratory Notebooks . ; 13-2
13.2 FIELD ACTIVITIES REPORT . 13-3
13.3 SAMPLE ANALYSIS REPORT- : . . 13-4
13.4 SAMPLE BATCH REPORTS ..................... 13-6
14.0 REFERENCES . . 14-1
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LIST OF FIGURES
Figure 3-1 Sample Collection and Field Preparation .. 3-2
Figure 3-2 Laboratory Preparation and Analysis ..-..' 3-3
Figure 8-1 Weighing a Soil Sample on a Field Scale 8-4
Figure 8-2 Weighing a Sample Split on a- Field Scale 8-6
Figure 8-3 Sieving a Soil Sample 8-7
Figure 8-4 A Riffle Splitter 3-8
Figure 8-5 Using a Riffle Splitter to .Homogenize/Split Samples 8-9
Figure 8-6 Loading a Sample Split into a Sample Bottle 8-11
Figure 8-7 Transferring Sample from a Mixer to a Plate for Coning and Quartering ... 8-13
Figure 8-8 Coning and Quartering '..'.. 8-14
Figure 11-1 Typical Cumulative Mass Release Versus Time Curve for a 30 RPM Run . . 11-6
Figure 11-2 Typical Cumulative Mass Release Versus Time Curve for a 60 RPM Run . . 11-7
Figure 11 -3 Illustration of the Optimization of the Estimate of Initial Mass "M0" ....... 11-9
Figure 13-1 Format for the Field Activities Report 13-5
Figure 13-2 Sample Analysis Report Format 13-7
Figure 13-3 Sample Batch Report Format 13-10
Figure A-1 Schematic of Dust Generator . A-2
Figure A-2 The Dust Generator A-3
Figure A-3 Tumbler in Constant Humidity Chamber A-4
Figure A-4 Tumbler Assembly . A-5
Figure A-5 Main Body of Vertical Elutriator '.-... A-8
Figure A-6 Bottom Assembly of Vertical Elutriator . ... A-9
Figure A-7 . Top Assembly of Vertical Elutriator . . . A-10
Figure A-8 Dust Collection System A-12
Figure A-9 Filter Mounts A-13
Figure A-10 Tubing Connections for the Scrubber of the Dust Generator . A-15
Figure A-11 Tubing Connections for Filter Cassettes Mounted on the Elutriator of the
Dust Generator ...... A-16
Figure A-12 Detail of Tubing Connections at the Top of the Vertical Elutriator ..... A-17
Figure A-13 Overall Prototype Dust Generator Assembly A-23
Figure A-14 Prototype Tumbler Assembly Detail A-24
Figure A-15 Prototype Vertical Elutriator Detail , ... A-26
Figure A-16 Section of Elutriator Top with Extension Tube A-27
Figure A-17 Longitudinal and Transverse Sections of Isokinetic Sampling Tube A-28
Figure A-18 Prototype Slide Mechanism Detail A-29
Figure A-19 Detail of Prototype Filter Cassette Mount? . A-30
VI
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1.0 INTRODUCTION
This is a sampling and analysis method for the determination of releasable asbestos in soils
and bulk materials. Samples are collected in a manner suitable for providing representative
measurements of the releasable fraction of asbestos in the matrix sampled, prepared using a
dust generator, and analyzed by transmission electron microscopy (TEM). Guidelines for
constructing the required dust generator are. also included.
During dust generation, the respirable fraction of the dust generated from the sample is
collected on filters. The filters are then weighed and the cumulative mass of dust collected is
plotted against time to determine the rate of release of dust. Results are extrapolated to
provide an estimate of the total mass of respirable dust in the original sample. The asbestos
released during dust generation fs either collected on a filter or in the suspension of a
scrubber (or both), depending on the configuration under which the dust generator is
operated. Filters may be prepared for TEM analysis by either a direct or an indirect transfer
technique. Preparation of the'scrubber suspension for TEM analysis is equivalent to an
indirect transfer procedure. Depending on the intended use of the data, the results of
asbestos analyses from this method may be reported either in terms of the number of
structures per unit mass of respirable. dust generated from the sample or the number of
structures per unit mass of the original sample.
The method allows for the determination of the mineralogical type(s) of asbestos that is
present in the sample and for distinguishing asbestos structures from non-asbestos
structures. In this method, asbestos structures are characterized as fibers, bundles, clusters,
or matrices and the length and width of each asbestos structure are measured. Although the
method is designed specifically to provide results suitable for supporting-risk assessments at
Superfund sites, it may be applicable to a wider range of studies.
As reported in this document, the method focuses on requirements for the collection,
preparation, and analysis of samples obtained from individual locations. During a site
investigation, samples will typically be collected from multiple locations that are arranged in
an array designed to provide measurements suitable for deriving a representative (i.e.
unbiased) estimate of the .concentration of releasable asbestos over the sampled matrix as a
whole. Thus,. proper design of a comprehensive sampling strategy, which includes the
detailed design of the array of sampling locations, is also critical to the success of an
investigation. However, design of a sampling strategy is necessarily site specific and site-
specific considerations are beyond the scope of this document. For further guidance on
developing appropriate sampling strategies, see Bermah and Chesson (undated).
This method has not yet been validated. Validation requires completion of a field study in
which airborne exposure concentrations of asbestos caused by the release and transport, of
asbestos from soils or bulk materials (under specific conditions) are related to the bulk
measurements of asbestos derived from this method. However,, while such a study is in
progress, this method has already been successfully tested in the laboratory. Such tests
. have demonstrated that the method is .capable of achieving adequate sensitivity and precision.
, to support risk assessment. The method also provides asbestos measurements that preserve
the information on the sizes and shapes of asbestos structures that are required to assess
risks. Thus,'the principle features of the method are well enough established to allow it to be
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employed in current field investigations. At the same time, until the formal validation study is
completed, this should.be considered an interim method.
NOTE ,
This document is intended to serve several audiences including site project managers,
field sampling teams, data reviewers, and laboratory analysts. The document may be
separated into segments so that individuals may focus on the sections of most interest
to their particular roles on a project.
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2.0 BACKGROUND
This method was developed specifically to satisfy the needs of the Superfund program
including: , .
the need to provide results suitable for supporting risk assessment;
the need to be applicable to the types of asbestos-containing materials
commonly encountered at Superfund sites; and
the need to facilitate reproducibility within and between laboratories that may
offer the method commercially. '
An additional consideration addressed during the development of this method is the need to
control sampling and analysis costs.
The first item listed above is what distinguishes sampling and analysis methods adapted for
use in the Superfund program from methods used in other programs. This is because the
statutory requirements of the Superfund program mandate that risk management decisions be
based oh risk assessment. Risk assessment requires that analytical data be relatable to
health effects. Although the remaining requirements listed above are also important, the first
item is a central feature of the Superfund program.
Because this method is designed for supporting risk assessment, the results of analyses from
this method are intended to be used as inputs to release and transport models to predict
airborne asbestos exposure concentrations (see Section 2.2). This is a very different
objective from existing bulk asbestos methods, which are designed as qualitative tools for
determining whether asbestos is present in a particular matrix in excess of a defined,
regulatory limit. For such methods, the regulatory limits are defined operationally as functions
of the methods themselves and, therefore, do not necessarily relate in any direct fashion to
the potential for asbestos to be released and contribute to risk.
2.1 REQUIREMENTS FOR A METHOD DESIGNED TO SUPPORT RISK ASSESSMENT
A feasibility study (Berman 1990) was completed both to identify the requirements of a
method for the determination of asbestos in soils and bulk materials that could be used to
support risk assessment and to evaluate existing sampling and analysis technologies to
determine whether such a method might be readily developed. Results of the feasibility
study indicate that, to support risk assessment under Superfund, the method must:
achieve sufficient analytical sensitivity to adequately measure asbestos over the
entire1 range of concentrations that might potentially pose an unacceptable risk;
provide adequate precision over the range of asbestos concentrations of interest;
provide measurements of the complete range of the sizes and shapes of
asbestos structures that are believed to contribute to health effects;
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provide measurements that are representative of the fraction of asbestos that is
readily releasable1 from the matrix of interest; and
provide results reported in units that are amenable for use as inputs to fate and
transport models that can be used to relate (bulk) source concentrations of
asbestos to (airborne) exposure point concentrations of asbestos.
2.1.1 Sensitivity ,
Based on calculations presented in the feasibility study completed for this method (Berman
1990), asbestos concentrations in soil or a bulk environmental matrix .that are on the order of
3x10 long asbestos s/gso|jd (i.e. 30 million asbestos structures longer than 5 jim per gram of
solid) or 5x108 total asbestos s/gsoljd (i.e. 0.5 billion total asbestos structures per gram of
solid) may potentially pose a risk exceeding 1 x 10"6. This is based on evaluation of a series
of scenarios in which asbestos is released from the solid matrix due to any of several types of
disturbance (i.e. vehicular traffic on the surface, agricultural tilling, or natural weathering).
Once released, asbestos is dispersed into the air, where exposure may occur. Note that, for
a typical chrysotile matrix, the concentrations reported above for the two different size ranges
of structures are expected to be approximately equivalent (i.e. concentrations observed for
each of the two size ranges in a sample containing common chrysotile are expected to be
approximately proportional to the two values given so that a sample observed to exceed one
will also likely exceed the other). Therefore, either concentration might serve as an adequate
target sensitivity for chrysotile. However, such may not be the case for all asbestos-
containing matrices, particularly those containing amphibole asbestos.
To assure that negative results from a soil-bulk method do not mask potential problems,
ideally, the analytical sensitivity for the method should be set at one tenth of the
concentrations potentially capable of producing risks that exceed 1 x 10"
target analytical sensitivities for this method have been set at:
Therefore, the
3x10 long asbestos s/gso|id (i.e. 3 million asbestos structures longer than 5 urn
per gram of solid); or
5x107 total asbestos s/gsoljd (i.e. 50 million total asbestos structures per gram of
solid).
The analytical sensitivity is reported for the two different size ranges of asbestos structures to
allow flexibility in the application of the method,
2.1.2 Precision
The only precision data currently available for this method is from the recently described pilot
study (Berman et al. 1994a). To establish a reasonable goal for the precision of this method,
a study of the precision achievable by commercial laboratories performing the method would
be required. Because data;from commercial laboratories are not available, the data from the
As used here, 'readily releasable" means particles that have already been separated into respirable size and that are
available in a poo! of loose material that can be released directly during some type of disturbance. This is
distinguished from particles that may be aggregated with others and that may be separated from the aggregate for
future release. -
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pilot study (Berman et al. 1994a) were evaluated to provide a rough estimate of the level of
precision potentially achievable once the method is commercialized (see Section .12.1.2).
Results suggest that a relative percent difference of 50%; should be easily achievable for
sample splits performed by. a single laboratory.
The USEPA has set informal precision guidelines for each of the analytical methods employed
in the contract laboratory program (CLP), under which the majority of sample analyses have
been conducted for the Superfund program. These goals tend to be defined as achievable
relative percent differences for sample splits "performed within a laboratory and they range
between 10% and 35% for the analysis of inorganic chemicals in soils and up to 50% for the
analysis of organic chemicals in soils. Therefore, given the above, a guideline of 50% for the
relative percent difference between sample splits performed within a laboratory is proposed
for this method.
2.1.3 Asbestos Characteristics '
Based on what is known about the biological activity of asbestos (for a critical review of the
extensive literature on this subject, see Berman and Crump 1989), if asbestos measurements
are to be related to risk, it is necessary to characterize the sizes, shapes, and mineralogy of
the asbestos structures in each sample. This involves enumeration of individual structures
within certain size categories with particular emphasis on the longest and thinnest structures.
Although the range of dimensions over which asbestos structures contribute to biological
activity has yet to be precisely defined, this method is designed to provide a detailed
characterization of structures encompassing the entire range of potential importance.
Results of the feasibility; study for this method (Berman 1990) indicate that transmission
electron microscopy (TEM) is the only analytical tool capable of characterizing asbestos
structures over the entire range of sizes and shapes that potentially contribute to risk.
Consequently, the asbestos derived from soil or bulk samples is analyzed using TEM in this
method. ,
When evaluating detailed asbestos size characterizations, it is important to consider the
effects of sample preparation. The dust generator incorporated into this method was
developed.because its use eliminates the need to employ other preparation techniques (such
as crushing or grinding) that potentially alter the distribution of respirable asbestos structure
sizes and shapes found in the sample. The dust generation employed in this method is a
gentle process; it is expected to preserve the distribution of asbestos structure sizes and
shapes that may be released to the air-when asbestos-containing media are disturbed in the
environment. , ..' ,
The size distribution of asbestos structures found in the dusts generated using this method
may also vary depending on whether TEM specimen grids are prepared from the dust;
samples, using a direct or an indirect transfer technique. Existing risk factors are based
largely on studies incorporating the equivalent of direct transfer techniques,2 while indirect
transfer techniques are expected to provide increased precision (see, for example, Berman
Most of the epidemiology studies (from which estimates of asbestos potency are derived) .employed either phase
contrast microscopy (PCM) for the analysis of asbestos concentrations in work place air or converted other types of
measurements to PCM equivalents (Berman and Crump 1989). PCM analyses are performed directly on sample filters
after the filter material has been rendered transparent by a suitable solvent. Since the fibers are observed as originally
deposited, this corresponds closely to a direct transfer technique for TEM analysis.
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and Chatfield 1990). Hence, this method incorporates a procedure,by which the majority of
samples, are prepared by an indirect technique with a subset prepared in tandem by a direct
technique. This facilitates evaluation of the relationship between structure counts derived
from samples prepared, respectively, by each technique.
2.1.4 Reporting Requirements
It is anticipated that soil or bulk samples to be analyzed using this method will typically be
collected to determine the asbestos content of a potential source from which asbestos may
be released (via a particular mechanism) and transported to the air (where exposure may
occur). It is also expected that asbestos release and transport will be modeled and that one
of the critical inputs to such models will be the concentration of releasable asbestos in the
source matrix. .
Results of the feasibility study for this method (Berman 1990) indicate that most of the
available models that predict releases to the air from soil or some other bulk matrix (in
association with specific release mechanisms) were designed to predict the release and
transport of respirable dust. Only a very limited number of such models have actually been
developed specifically for asbestos. The dust models may be used to predict asbestos
release and transport with minimal modification, however, provided that the appropriate types
of asbestos measurements are available. Such adaptations rely on the following
assumptions:
the rate,of settling of respirable asbestos particles is no more rapid than the
average settling rate for respirable dust; and
the release of asbestos and the release of respirable dust from a source matrix
are highly correlated (i.e. are proportional), at least over the long term.
The former assumption is expected to be true because fibers tend to settle more slowly in the
air than spheres of comparable mass. The latter assumption appears reasonable because, if
it were false, one would expect the source matrix to become either enriched or depleted in
asbestos over time. However, such effects are not generally observed.
Many of the release models developed for respirable dust require the mass fraction of silt in
the source matrix as an input parameter. For such models, substituting the fiber
concentration of asbestos (per unit mass of source matrix) for the mass fraction of silt should
allow the model to be used to predict asbestos release (with no additional modifications).
Under such circumstances, a dimensional analysis of the model should indicate that the
outputs would now be expressed in terms of the number of asbestos structures released from
a defined area (or mass) of the source matrix per unit time (rather than the mass of respirable
dust released from a defined area or mass of the source matrix per unit time). Such outputs
are then typically combined with air dispersion models to predict airborne concentrations at
locations (i.e. points of exposure) of interest.
As an alternative, it may, be useful to multiply the respirable dust release rates, (that are
predicted by a model) by a factor representing the number of asbestos structures (of a size
range of interest) per unit mass of respirable dust released from the sample. For certain
models, this approach for"converting a dust model to an asbestos release model may prove
easier than the approach discussed above.
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This method is designed to provide results that can be reported as the number of asbestos
structures (of a size range of interest) per unit mass of source matrix with an option allowing
the reporting of the number of asbestos structures per unit mass of the respirable dust
released from the sample. The appropriate reporting option should be selected based on the
specific models with which the -measurements from this method are anticipated to be used for
a specific project. , -
NOTE
This method may also be used to provide an independent (qualitative) check of the
predictions of specific release models in some cases. In one of the intermediate steps
of this method, the rate of release of respirable dust from the sample is determined.
This can be compared to the rate of release predicted by a release model. The
relative magnitude of the release rate observed using this method and the release rate
predicted by a model should be consistent with that expected based on the relative
aggressiveness of the type of disturbance applied to the sample' during measurement
using this method and the type of disturbance associated with the field activity (i.e.
vehicular traffic, excavation, wind entrainment, etc.) represented by the model.
2.2 ASBESTOS CONTAINING MATERIALS TYPICALLY ENCOUNTERED AT
SUPERFUND SITES
Asbestos containing materials commonly encountered at Superfund Sites include:
natural rocks that contain asbestos;
soils containing natural asbestos generated from weathered rock;
« soils containing asbestos introduced by transport from other locations;
mine or mill tailings (i.e. fractured or depleted rock); .
discarded asbestos wastes, including,(for example):
, - asbestos/cement pipe; ,
roofing materials; ,
insulation materials;, and
soils containing discarded asbestos wastes. -. .
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This method is designed specifically to handle the above materials (with the exception of
unfractured rock ) and may be applied generally to samples of any unconsolidated or
friable4 matrix.
2.3 REQUIREMENTS FOR FACILITATING REPRODUCIBILITY BETWEEN
LABORATORIES
Results of the feasibility study for this method (Berman 1990) indicate that, for a method for
the determination of asbestos in soils and bulk materials to adequately facilitate
reproducibility between laboratories that might offer trie method commercially, the following
requirements must be satisfied:
preparation steps in the procedure have to be kept simple and must be
standardized and documented sufficiently to allow technicians in different
laboratories to perform them invariably (i.e. objectively); and
the representativeness of a sample (i.e. the degree with which the sample retains
the characteristics of the matrix from which it is derived) has to be preserved
throughout all stages of handling, preparation, and sub-sampling that are
incorporated into the method.
To address each of the above requirements, the ability to homogenize the sample has to be
maintained throughout all stages of sample preparation and handling, and dust generation
satisfies these requirements. In addition, dust generation is incorporated into this method as
the means of extracting the respirable fraction of releasable asbestos from bulk samples in a
manner that can be performed invariably; it is a mechanical process that can be controlled
objectively by specifying the design and the operation of the equipment to be used for dust
generation. '
Use of a dust generator eliminates most of the sample manipulation steps typically performed
manually (and subjectively) for other bulk asbestos methods. More importantly, it eliminates
the need for sub-sampling of amounts smaller than approximately 100 g, which is a mass that
is large enough to be sub-sampled reproducibly (by following specified procedures). A 100 g
sample is also sufficiently large to retain representative characteristics of all components of a
sampled matrix in which the particles are smaller than approximately 1 cm in diameter.
Results of the feasibility study (Berman 1990) indicate that the ability to homogenize an
unconsolidated bulk sample (in preparation for sub-sampling) is a direct function of the
largest particle in the distribution of component particles; to allow representative sub-sampling
of such a matrix, the largest particle must represent no more than a few percent of the total
mass of the sample. Therefore, because the final sub-sample to be extracted in this method
is on the order of 100 g, the largest particles that can remain in-the sample prior to sub
It is assumed that any asbestos imbedded in unfractured rock can be considered to be non-releasable. If there is a
desire to evaluate the release of asbestos from the surface of such rock (or the potentialfor release of asbestos from the.
rock as it becomes fractured in the future due to aging or disturbance), conceivably, a sample of the rock might be
crushed to particles no larger than 1 cm in diameter (see text) and a sample of the crushed rock might then be
analyzed using this method. However, no formal protocol has been developed for this procedure at this time.
As used here, the term friable is intended to mean any material that can be crushed or deformed with the hand with the
attendant release of fibers.
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sampling must be no larger than 2 or 3 g. Assuming a typical density for silica type materials
(i.e. 2.6 g/cc), the largest particle,that can be retained while allowing 100 g samples to remain .
representative of the sampled matrix is 'approximately 1 cm (3/8th inch) in diameter
(4/3nr3*density = 1.4 g). Consequently, this method incorporates a step in which samples
are sieved to remove particles larger than 1 cm in diameter5.
It must be emphasized that the particles larger than 1 cm in diameter that are removed from
the sample by sieving in this method are not discarded. Rather, both the fraction passed by
the sieve and the fraction retained by the sieve are weighed and the weights recorded so that
the asbestos content measured can ultimately be reported as a function of the total mass of
the initial sample (i.e. the asbestos concentration measured in the method is multiplied by the
ratio of the total mass of the original sample collected and the mass of the fraction of the
sample analyzed). The larger particles do not need to be carried through the entire analysis,
however, because it is, unlikely that significant amounts of the. releasable asbestos in a
sample reside in the coarse fraction. '
2.4 COST CONSIDERATIONS
To,be. useful,, it was determined that the cost of an individual analysis using this method
would have to be competitive with other methods that might be used to derive comparable
information.6 In fact, once a laboratory invests in the construction of a dust generator to
support the method and procures the required ancillary equipment, it is expected that the
cost of analysis using this method will be very competitive with other soil or bulk methods
(that might be designed to provide similar information). This is because use of the dust
generator effectively concentrates asbestos from the sample (by removing the non-respirable
component). ^Sueh concentration allows highjpr Joadings on specimen grids so that smaller
areas need to be scanned with the TEM to complete an analysis.
It is expected that sample preparation using the dust generator will cost approximately $400
(twice what it costs to complete the preparation of an air sample using an indirect transfer
technique). This cost, however, is expected to be more than compensated by the
corresponding reduction in cost for TEEM scanning time, which is reduced due to the ability to
scan more highly concentrated samples (see above). It is therefore expected that the total
cost of an analysis using this method may run between $900 and $1,500, which should be
competitive with any other soil or bulk method that is designed to provide comparable
information. This cost is approximately 10 to 15% higher than that for the analysis of an air
sample in which comparable structure size information is recorded.
Incorporated into this method (as an option) is a compositing procedure that can be used to
reduce significantly the number of bulk analyses that might otherwise be required to
adequately characterize a source matrix from which asbestos may be released (Section 8.3).
Recognizing that airborne exposure due to emissions from a, source matrix tend to be the
result of average emissions, over .relatively large areas, compositing of samples is a
The dust generator designed for this method best handles samples up to a maximum of approximately 80 g. However,
the practical difference between 80 and 100 g samples, in terms of the maximum size of the particles that can be
retained (while assuring.the ability to homogenize the sample), is not significant.
This assumes analysis using TEM in which comparable size and mineralogy information is recorded; methods in which
analysis is performed by polarized light microscopy (PLM) are not capable of providing information over the complete
range of structure sizes and shapes that are believed to relate to risk. -
. ' ' ' 2-7 = ' - "'...
-------
particularly powerful tool that can be. used in tandem with this method. By reducing the
number oJ sample analyses required to adequately characterize a particular source, the cost
of a particular investigation can be reduced correspondingly.
An additional cost saving measureJncorporated into this method is completion of the early
stages of sample preparation in the field. This simplifies the handling and preparation
performed by the laboratory and limits the size (mass) of each sample that has to be stored
or disposed by the laboratory. .
Handling and preparation of bulk samples in the laboratory are dusty operations that require
protective enclosures. The larger the sizes of the samples, the larger the protective
enclosures required. Additionally, asbestos containing samples handled by a laboratory must
be disposed as asbestos wastes. Clearly, the larger the mass of such samples handled by
the laboratory, the greater the cost of disposal.
2-8
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3.0 OVERVIEW OF METHOD
Samples are collected in the field according to a pre-defined sampling plan identifying the
number of samples to be collected and the locations from which samples are to be collected.
Procedures for designing such a plan are beyond the scope of this document but are
reported elsewhere (see, for example, Berman and Chesspn, undated).
Any of a variety of commercially available sampling equipment (i.e. trowels, shovels, augers,
corers, etc.) may be used to collect samples for this method. However, they must have been
specified in the pre-defined sampling plan based on the nature of the material being sampled
and the depths over which samples are to be collected. Whatever sampling technique is
employed, the minimum size sample to be collected at each location shall be 1 kg.
Once collected, each sample is brought to a central location for field preparation. Field
preparation steps are listed in Figure 3-1 arid discussed in detail in Chapter 8. Each sample
is first weighed (Section 8.2.1). Then the sample is sieved .using a screen with 3/8th in.
(1 cm) openings to separate a coarse and fine fraction. The material placed on the sieve is
worked with gloved hands to assure that all friable components pass through the screen
(Section 8^2.2).
The coarse fraction, composed of material that is retained by the screen, is transferred to a
bucket and weighed prior to discarding on site. The fine fraction, is also Weighed. As
indicated in Figure 3-1, the fine fraction is then homogenized. The procedure recommended
in this method for hornogenization is repetitive splitting using a riffle splitter with the split
halves of the sample being re-combined at the end of each split (Section 8.2.3). Studies
indicate that five to seven .iterations are typically sufficient to achieve adequate
hornogenization. .
Once homogenized, the fine fraction is then sub-sampled using the riffle splitter (Figure 3-1).
During sub-sampling, the one-half of the sample from one of the two receiving trays is
discarded after each split (Section 8.2.3) and the second half of the sample, is then re.-split.
The process is repeated until sub-samples weighing between 50 and 80 g are produced in
each of the two receiving trays. The material in each tray is then transferred quantitatively to
a sample bottle, packaged and shipped to the laboratory.
Sample handling, preparation, and analysis in the laboratory is depicted in Figure 3-2 and
described in detail in Chapter 9. Once sub-samples weighing between 50 and 80 g are
obtained, they can be separately prepared and analyzed (Section 9.2).
,To prepare samples, as indicated in 'Figure 3-2, first load the sample into the tumbler of a
dust generator. The design, construction, and operation of a dust generator suitable for use
with this method is provided in appendix A. .The sample is then conditioned by flowing
humidity-contrplled air through the tumbler and over the sample for several hours (Section
9.4.2). ' '.-'. ' .'..'..
Once the sample is conditioned, the tumbler of the dust generator is started and a sample
run is initiated (Section 9.4.3). During each run, a series of filters is collected continuously
from the top of one of the openings of the dust generator and these are weighed to plot the
cumulative dust loss from the samplex(Section 9.4.4 and the right side pathway of Figure 3-2).
3-1
-------
FIGURE 3-1
SAMPLE COLLECTION AND FIELD PREPARATION
SURVEY SITE:
IDENTIFY SAMPLING LOCATIONS
COLLECT SAMPLES
FOR EACH SAMPLE
WEIGH SAMPLE
FINE FRACTION
{< 1 CM. DIA.)
SIEVE SAMPLE
COARSE FRACTION
(> 1 CM. DIA.)
WEIGH FRACTION
WEIGH FRACTION
HOMOGENIZE
DISCARD ON SITE
WEIGH FRACTION
SPLIT
DISCARD SPLIT
WEIGH SPLIT
SPLIT
DISCARD SPLIT
SUB-SAMPLING
REPEAT AS REQUIRED
UNTIL FINAL SPLITS
WEIGH BETWEEN
50 AND 80 G.
WEIGH SPLIT
BOTTLE AND LABEL
FOR TRANSPORT
TO LAB
BOTTLE AND LABEL
FOR TRANSPORT
TO LAB
-------
. FIGURE 3-2
LABORATORY PREPARATION AND ANALYSIS
RECEIVE SAMPLE FROM
.THE FIELD
Yes
HOMOGENIZE
DOES
SAMPLE
WEIGH MORE
THAN
80G?
SPLIT SAMPLE
LOAD DUST GENERATOR
CONDITION SAMPLE
SCRUBBER
SUSPENSION
I
RUN DUST GENERATOR
FILTER SUSPENSION
FILTERS COLLECTED
FOR DUST ANALYSIS
FILTERS
COLLECTED
FOR DIRECT
ASBESTOS
ANALYSIS
PERFORM
GRAVIMETRY
PREPARE TEM
SPECIMEN GRIDS
PERFORM
TEM ANALYSIS
PLOT CUMULATIVE DUST
LOSS FROM SAMPLE
ESTIMATE MASS OF
DUST ON FILTERS
USED FOR
ASBESTOS ANALYSIS
DETERMINE
CONCENTRATIONS OF
SIZE-SPECIFIC
ASBESTOS STRUCTURES
IN RESPIRABLE DUST
DETERMINE
CONCENTRATION OF
RESPIRABLE DUST IN
SAMPLE
DETERMINE
CONCENTRATIONS OF
, VSIZE-SPECIFIC
ASBESTOS STRUCTURES
IN ORIGINAL SAMPLE
-------
While the dust generator is operating, a second set of filters is also collected over the
opening.of the dust generator that articulates with an isokinetic sampling tube (the center
pathway of Figure 3-2). These are collected such that loading is appropriate for specimen
grid preparation using a direct transfer technique (Section 9.4.5).
Asbestos structures are also trapped in the suspension of a scrubber during each run of the
dust generator (the left side pathway of Figure 3-2). The suspension is then diluted
appropriately and filtered to create an additional set of filters from which specimen grids will
be prepared for asbestos analysis (Section 9.4.6). However, because asbestos structures
derived from this process will have been suspended in the aqueous environment of the
scrubber suspension, preparation of grid specimens from filtered scrubber suspension are
considered to have been prepared in a manner that is equivalent to an indirect transfer
technique.
Next, as indicated in Figure 3-2, TEM specimen grids are prepared using a direct transfer
technique from the filters collected either from atop the isokinetic sampling tube of the
elutriator or from filtering scrubber suspension (Sections 10.1 and 10.2). Specimen grids are
then analyzed using the counting and identification rules of the International Standards
Organization (ISO) Method for the determination of asbestos in air using an indirect transfer
technique (Chatfield 1993) with the stopping rules modified as indicated in Section 11,1.
Calculations are performed from plots of the cumulative dust loss (Section 11.2) to estimate
both the mass of dust co-collected with asbestos on the filters prepared for asbestos analysis
and the total mass of respirable dust in the original sample. Dust estimates are then
combined with asbestos counts to allow reporting of both the concentration of asbestos
structures per unit mass of respirable dust in the sample and the concentration of asbestos
structures per unit mass of the original sample (Figure 3-2)7. Typically, asbestos
concentrations will be reported from this method for a specific size range of asbestos
structures of interest.
When asbestos concentrations are to be reported as a function of the mass of the original sample, the concentration
calculated in the laboratory, which represents the concentration of asbestos in the fine fraction of the original >ample,
must ultimately be adjusted to account for the mass of the coarse fraction of the sample as well (Section 11.4.3).
3-4
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4.0 DEFINITIONS
Amphibole: a group of rock-forming ferromagnesium silicate minerals, closely related in
crystal form and composition, and having the nominal formula:
A0-1B2C5T8022(OH.F'CI)2
where: - t . ,
A = K, Na; : ., " '
B = Fe2+, Mn, Mg, Ca, Na; . . .'' ' ' ,
. , j
C = Al, Cr, Ti,,Fe3+, Mg, Fe2+;
- T = Si, Al, Cr, Fe3+, Ti. !
- '' . l '
In some varieties of amphibole, these elements can be partially substituted by Li, Pb, or Zn.
Amphibole is characterized by a cross-linked double chain of Si-O tetrahedra with a silicon:
oxygen ratio of 4:11, by columnar or fibrous prismatic crystals and by good prismatic
cleavage in two directions parallel to the crystal faces and intersecting at angles of about 56°
and 124° (see Chatfield 1993). ,
.Amphibole Asbestos: amphibole in an asbestiform habit.
Analytical Sensitivity: the calculated asbestos concentration in soil or a bulk matrix, in
asbestos structures/g, equivalent to counting of one asbestos structure in the analysis.
Asbestiform: a specific type of mineral fibrosity in which the fibers and fibrils possess high
tensile strength and flexibility. .' . -.
''"'/-.
Asbestos: a term applied to a group of fibrous silicate minerals that readily separate into'
thin, strong fibers that are flexible, heat resistant and chemically inert. ' ,
Asbestos Component: a term applied to any individually identifiable asbestos sub-structure
that is part of a larger asbestos structure. , .
Asbestos Structure: a term applied to any contigupus grouping of asbestos fibers, with or
without equant particles. , . , ,
Aspect Ratio: the ratio of the length to width of a particle. _
Blank: a fiber count made on TEEM specimen grids prepared from an unused filter (or a filter
through which' asbestos-free water has been, passed), to determine the background
measurement. Blanks consist of filter blanks, field blanks and laboratory blanks. Laboratory
blanks for this method .may include scrubber blanks.
Bundle: a fiber-composed of parallel, smaller diameter fibers attached along their lengths
(see Chatifield 1993). " .' .
4-1
-------
Chrysotiie: the asbestiform habit of a mineral of the serpentine group that has the nominal
composition:
Mg3Si205(OH)4
In some varieties of chrysotiie, the silicon may be partially substituted by Al or less commonly
by Fe. The magnesium may be partially substituted by Fe, Ni, Mn or Co. Some varieties
contain Na, Cl or both. Chrysotiie is a highly fibrous and silky variety and constitutes the
most prevalent type of asbestos (see Chatfield 1993).
Cluster: an assembly of randomly oriented fibers (see Chatfield 1993).
Component Count: for any sample, a tally that includes the individually identified
components of complex asbestos structures and each single asbestos structure with no
identifiable components.
Elutriator: a device in which differential flow through a fluid (gas or liquid) against an
opposing force (i.e. gravity) is employed to separate particles by size.
Equant Particle: as used in this document, a non-asbestos particle bound to, or overlapping
with, asbestos structures observed on a TEM specimen grid.
Fiber: an elongated particle that has parallel or stepped sides. In this method, a fiber is
defined to have an aspect ratio equal to or greater than 5:1 (see Chatfield 1993).
Fibril: a single fiber of asbestos that cannot be further separated longitudinally into smaller
components without losing its fibrous properties or appearance.
Fibrous Structure: a contiguous grouping of fibers, with or without equant particles.
Field Blank: a filter cassette that has been taken to the sampling site, opened, and then
closed. Such a filter is analyzed to determine the background asbestos structure count for
measurement and to document the treatment of the filter from sample collection through
analysis.
Filter Blank: an unused filter that is analyzed to determine the background asbestos
structure count on the filter matrix. . . " ,
Friable: as used in this document, capable of being crushed or deformed with the hand with
the attendant release of fibers.
Habit: the characteristic crystal form or combination of forms of a mineral, including
characteristic irregularities. ,
Identify: during asbestos analysis, the use of a sequential set of procedures to determine
and confirm the mineralogy of a structure. ...
Isokinetic Sampling: sampling air in such a manner so as not to disturb the direction or
velocity of air flow at the point sampled.
4-2
-------
Isokinetic Sampling Tube: a tube placed in the air flow of the vertical elutriator portion of the
dust .generator used in this method, which samples the air at the top of the elutriator
isokinetically, '.';-
Laboratory Blank: an unused filter that is analyzed along with sample filters to determine the
background asbestos structure count in the laboratory.
N
Matrix:8 A connected assembly of asbestos fibers with particles of another species (non-
asbestos) (see Chatfield 1993).
PCM. Equivalent Structure: A structure of aspect ratio greater than or equal to 3:1, longer
than 5 jim, and which has a mean diameter between 0.2 jim and 3.0 \im for a part of its
length greater than 5 jim. In this method, PCME structures "also must contain at least one
asbestos component (see Ghatfield 1993). ,
Riffle Splitter: a device composed of a hopper and multiple, uniform, parallel chutes that
alternately feed from the hopper to opposing receiving trays. ^
Scrubber: a device for removing particles from an air stream by passing the air stream
through a super-saturated vapor in which the particles serve as nucleation centers for
condensation and are thus captured. The resulting droplets (containing the trapped particles)
then fall back into a central reservoir of boiling liquid.
Serpentine: a group of common rock-forming minerals having the nominal formula:
. . - ' Mg3Si205(OH)4 . .
Serpentine, deposits often contain chrysotile asbestos (which is serpentine in an asbestiforrrV
habit). ''-.'";'.
Structure Count: for any sample, a tally of each individually identified asbestos structure
regardless of whether the structure contains identifiable components. This is equivalent to> a
count of the total number of separate asbestos entities encountered on the sample.
Vertical Elutriator: see Elutriator. .
Tumbler: a-device that is rotated to provide continuous agitation to a bulk material placed
inside. In the dust generator employed Jn this method, air is blown through a tumbler
containing sample to carry away the dust generated during agitation by the tumbler.
When used to describe an asbestos structure. The term is also used in this document to ^describe .a heterogeneous
bulk solid. . ' , .
' ' -'.''. * 4-3 . ' ' ' ' .: ' ,
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-------
5.0 SYMBOLS AND ABBREVIATIONS
5.1 SYMBOLS
dust
smpl
CF
cm
cm2
cm3
cm3/min
d
DF
°C
°K \
AMf
AIVL
o
At
T
eV '
the area of a filter from which a specimen grid is prepared (mm ).
the average area of a specimen grid opening (mm2).
the concentration of asbestos structures (of a defined size and type) in
the respirabie dust from a sample (s/gdust).
the concentration of asbestos structures (of a defined size and type) in
the original field matrix that was sampled for analysis using this method.
the concentration of asbestos structures (of a defined size and type) jn a
soil or bulk sample (s/g). '
the coarseness adjustment factor representing the ratio of the mass of
the fine fraction to the total mass of a matrix that is sampled in the field.
centimeter (10~2 rneter).
square centimeter. ','.'.'. ;
cubic centimeter.
cubic centimeter per minute.
the density of a particle (g/cm3).
the dilution factor representing the ratio of the scrubber suspension
volume to the aliquot that is filtered to prepare specimen grids.
degrees centigrade.
degrees Kelvin.
.the mass of respirabie dust collected on a single filter.during the interval
At(g). ,i
the mass of respirabie dust released from the sample during the interval
At(g).
a short time interval (no more than 10 minutes).
the dynamic viscosity of air (g/cm*s).
f " -
electron volt.
5-1
-------
ft
g
i
g
g/L
g/cm3
hp
k
kg
kV
in
L
L/min
M,
coarse
M.
'f
Mf30
Mfine
M
the .rate of airflow (i.e. the volumetric flow rate) through the top exit (ME)
opening of the elutriator that does not pass through the isokinetic
sampling tube (cm3/s).
the rate of airflow (i.e. the volumetric flow rate) through the top exit (1ST)
opening of the elutriator that passes through the isokinetic sampling
tube (cm3/s).
the rate of airflow (i.e. the volumetric flow rate) through the scrubber
(cm3/s).
foot.
gram. -
the acceleration due to gravity (cm/s2), when used as a variable in an
equation.
gram per liter. ~ s
gram per cubic centimeter.
horsepower.
the first order rate constant (s~1).
kilogram (103 gram).
kilovolt.
inch.
liter.,
liters per minute.
the mass of the coarse fraction of a matrix sampled in the field.
the 'cumulative mass of respirable dust collected on filters from the start
of a run to time, t (g).
the cumulative mass of respirable dust collected on filters during an
entire 30 rpm run (g).
the mass of the fine fraction of a matrix sampled in the field.
the mass of respirable dust in a sample at the start of a run (g).
the cumulative mass of respirable dust released from a sample from the
start of a run to time, t (g).
5-2
-------
Ms
Mscrbr
sample
Mtot
ml
mm
mm2
N
go
N
'gon
nm
t
%RD
r2
ch
the mass of respirable dust remaining in a sample during a run but after
time, t (g). ,
the mass of respirable dust collected in the scrubber during a run (g).
the mass of a 'Sample introduced into the dust generator (g). ,'.
' ' - ' " /
the total mass of respirable dust estimated to reside in a sample (g).
millimeter (10~3 meters). . . , ' , .
square millimeter.
microgram (10~6 grams).
micrometer (10"6 meters).
the number of grid openings counted during a scan (#).
the number of grid openings counted during a high magnification scan
(#).
the number of grid openings counted during, a low magnification scan
' "
nanometer (10~9 meter).
the pressure measured at a flowmeter (torr).
\
the pressure estimated at an elutriator opening (torr).
the mass percent of respirable dust in a sample (%)
the radius of a particle (cm). , '
the coefficient of determination (also defined as the correlation
coefficient squared).
the flow reading from a flowmeter (cm/s). ,
the number of asbestos structures (of a defined size and type) counted
during a high magnification scan (#). .
the number of asbestos structures (of a defined size and type) counted
during a low magnification scan (#).
the number of asbestos structures that must be detected during a TEM
scan for asbestos to be defined as detected (#).
5-3
-------
smpl
s
S/g
S/L
S/mm2
t
Tf
T.
V.
a1
v
w
the required analytical sensitivity for this method (defined separately for
total and long asbestos structures) (s/g).
second.
structures per gram.
structures per gram of dust.
structures per liter.
structures per square millimeter.
time (s). ,
-\
the temperature at a flowmeter (°K).
the temperature at an exit opening of the elutriator (°K).
the volume of the first aliquot collected from the scrubber suspension to
be used for further dilution (ml).
the volume of the final aliquot collected from Vd, which is filtered for the
preparation of specimen grids for TEM analysis (ml).
the volume into which the first aliquot from the scrubber suspension is
diluted (ml).
linear air flow rate (cm/s).
the volume of scrubber suspension generated from a run (ml).
the volumetric air flow rate (cm3/s).
watt.
5.2 ABBREVIATIONS
ED - Electron diffraction
EDXA - Energy dispersive X-ray analysis
FWHM - Full width at half maximum
HEPA - High efficiency particle absolute
1ST - refers to the opening at the top of the elutriator that is associated with
the isokinetic sampling tube
MCE - Mixed cellulose ester
5-4
-------
ME - refers to the main exit opening at the top of the elutriator, which is not
associated with the isokinetic sampling tube
.PCM - Phase contrast optical microscopy
PCME - Phase contrast microscopy equivalent
PLM - Polarized light microscopy
RPM - Revolutions per minute .
SAED - Selected area electron diffraction .
TEM - Transmission electron microscopy
TSP - Total suspended particulate
"* r '
LJ1CC - Union Internationale Contre le Cancer
5-5
-------
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6.0 FACILITIES AND EQUIPMENT
6.1 SAMPLE COLLECTION EQUIPMENT AND CONSUMABLE SUPPLIES
To complete field sampling per this method, the following field equipment is mandatory:
survey equipment appropriate to the manner in which sample locations are to be
defined per the sampling plan;
appropriate trowels, shovels, augers, or corers for sample collection per the
sampling plan;
(when sampling surface materials) a 12 in square aluminum template with an 8 in
: square hole in the center; ;.." L
a minimum of three 3-gal plastic buckets;
a brass or steel sieve with 3/8 in. (1 cm) openings; '
a field balance (with a capacity of 40 kg and capable of achieving a precision of
± 10 g);
a field balance (with a capacity of 2 kg and capable of achieving a precision of
+ 0.2g)9 ,.' . ^
a riffle splitter with a minimum of 24, 3/4 in. (minimum size) chutes and three
sample trays;
one L plastic sample containers; ;
sufficient plastic coolers to store and ship samples at ice temperature;
equipment for cleaning sampling tools, including:
- large buckets and tubs;
; - , a container of asbestos-free water; >
- garden sprayers; , , ,
- bio-degradable detergent; . ,
- assorted asbestos-free rags, sponges, etc.;
an air compressor with HEPA filter (optional, for drying,equipment); L
field logbook and appropriate custody forms and sample labels;
assorted garbage bags, paper towels, and tape;
Tyvek suits and protective gloves; and x
If appropriate equipment is available, it is advantageous to use a single field balance to achieve both sets of capacity
and precision requirements for field weighing. , ,
, -. . . 6-1 ' ' .
-------
appropriate equipment for respiratory protection.
6.2 LABORATORY FACILITIES
Laboratories wishing to adopt this method must develop and maintain the following facilities:
a properly ventilated room for bulk sample handling that is entirely isolated from
other room(s) in which air samples are handled and asbestos samples are
analyzed. All such facilities must be sufficiently well ventilated to allow
preparation of blanks that yield background determinations satisfying the
requirements of Section 10.6 of the Superfund air method (Chatfield and Berman
1990);
a glove box or equivalent isolation chamber of sufficient size to house a riffle
splitter (or other equipment) required for the homogenization and sub-sampling of
samples for this method. The glove box or isolation chamber must provide
ample room for handling kg size soil or bulk samples while maintaining
background concentrations in the outside room air at levels considered
acceptable as defined in Section 10.6 of Chatfield and Berman (1990);
a dust generator constructed per the specifications provided in Appendix A;
a TEM operating at an accelerating potential of 80-120 kV, with a resolution
better than 1.0 nm and a magnification range of approximately 300 to 100,000.
The ability to obtain a direct screen magnification of about 100,000 is necessary
for inspection of fiber morphology; this magnification may be obtained by
supplementary optical enlargement of the screen image by use of a binocular if it
cannot be obtained directly. The TEM shall also be equipped with an energy
dispersive X-ray analyzer capable of achieving a resolution better than 175 eV
(FWHM) on the MnKa peak. For requirements concerning screen calibration and
SAED and ED performance, see Chatfield and Berman (1990); and
a computer system for recording analytical results. As indicated in the section
addressing reporting requirements (see Chapter 13), analytical results are to be
provided on computer disk (either 3.5 inch or 5.25 inch in double sided or high
density format) in a file format that is compatible with LOTUS. ASCII files are
acceptable.
6.3 THE DUST GENERATOR AND APPURTENANT EQUIPMENT
The dust generator is to be constructed per the design drawings and specifications provided
in Appendix A. Appurtenant equipment required to support the dust generator includes:
a 129 hp DC motor (rated for 0 to 139 rpm) to drive the tumbler;
two vacuum pumps capable of drawing 20 L/min at minimum load (will be run at
1 to 2 L/min); '
6-2
-------
two variable area flowmeters capable of reading volumetric airflow velocities up to
1500 ml/min and one variable area flowmeter capable of reading airflow up to
, 250 ml/min; : . u "' ' ' '
a heating mantle and variable voltage transformer suitable for maintaining water
at a boil in, a 1 L round bottom flask; and
an immersion pump and cooler (or equivalent system) of sufficient capacity to
provide 0° C water at a rate of 1 -to 2 L/min.
6.4 SPECIMEN PREPARATION EQUIPMENT
As defined in the ISO Method for the determination pf asbestos in air using an indirect
transfer technique (Chatfield 1993). . , .
6.5 OTHER LABORATORY EQUIPMENT
As defined in the ISO Method for the determination of asbestos in air using an indirect
transfer technique (Chatfield 1993).
6.6 CONSUMABLE/REUSABLE LABORATORY SUPPLIES
For each run of a sample using the dust generator:
a lot of fifty MCE filters (0.45 urn pore size, 25 mm) that exhibit no more than
10 s/mm2 asbestos as background ; and
forty plastic petri dishes for storing 25 mm filters. ,
Also, other items as defined in the ISO Method for the determination of asbestos in air using
an indirect transfer'technique (Chatfield 1993)11.
.10 -This 'value is selected to assure that detection of a single structure in 4 grid, openings is more likely than not to
constitute asbestos from a samp.le. , , . , .
,11
This includes a supply of MCE filters (0.22 /im pore size) for filtering scrubber suspension.
-------
-------
7.0 REAGENTS
To support use of the dust generator, the following reagents are required:
asbestos-free water (a regular supply of freshly distilled, filtered water must be
available);
potassium carbonate dihydrate (analytical grade)12; and
sodium hexametaphosphate (analytical grade).
Also, reagents required to support asbestos analysis are defined in the ISO Method for the
determination of asbestos in air using an indirect transfer technique (Chatfield 1993).
WARNING - USE ALL REAGENTS IN ACCORDANCE WITH THE APPROPRIATE HEALTH
AND SAFETY REGULATIONS.
This salt is required for loading, into the constant humidity chamber and the desiccators to be used for conditioning
filters under the recommended default conditions for running the dust generator. A supply of alternate salt (analytical
grade) may be employed for studies in which dust generation is to be performed at a relative humidity other than the
default recommendation (see Section 9.3.2). '
' '.- ' "' 7-1
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8.0 SOIL OR BULK SAMPLE COLLECTION
Sample collection procedures adopted for this method are flexible to allow adequate sampling
of a broad variety of matrices. The method also incorporates several,field preparation steps.
that are designed to preserve sample representativeness while reducing the mass of the
samples sent to a laboratory for analysis. Controlling the mass of the samples sent to a
laboratory from the field is a cost saving measure (see Section 8.2).
WARNING:
MOST OF THE SAMPLE COLLECTION PROCEDURES AND FIELD PREPARATION
PROCEDURES DISCUSSED IN THIS DOCUMENT ARE INHERENTLY DUSTY
OPERATIONS. THEREFORE, WHEN HANDLING SOILS OR BULK MATERIALS
THAT ARE KNOWN TO CONTAIN OR POTENTIALLY CONTAIN ASBESTOS, IT IS
IMPERATIVE THAT PROPER RESPIRATORY PROTECTION BE WORN WHILE
CONDUCTING THESE PROCEDURES.
8.1 SAMPLE COLLECTION
Any variety of commercially available field sampling equipment (trowels, shovels, augers,
corers, etc.) may toe used to collect samples for this method. The equipment and
procedure(s) selected should be based on the nature of the material being sampled and the
depths over which samples are to be collected. Two common examples are presented
belpw., Whatever equipment and procedures are chosen, however, shall be applied
consistently and invariably at each sampling location13.
Whatever technique is chosen, the minimum size sample that shall be collected at each
sampling location shall be 1 kg. Larger samples may be required, however, if particularly
large (i.e. larger than a 4 or 5 cm in diameter) rocks or debris are. present in the material
being sampled. To assure representativeness, the largest component sampled should
occupy no more than a few percent of the volume of the sample collected (Section 2.3). If
samples are to be composited (Section 8.2), they shall be of similar mass (i.e. differences in
mass between composited samples shall be no larger than 10% of the mass of the smallest
sample). ( '
Locations from which soil or bulk samples are to be collected shall be selected formally as part of a comprehensive
strategythat is designed to provide a representative (unbiased) set of measurements for characterizing the releases of
asbestos from the entire source matrix of interest. Procedures for designing such a strategy are beyond the scope of
this document but are available elsewhere (see, for example, Berman and Chesson undated).
It is particularly critical, when collecting samples for soil or bulk asbestos analysis, to minimize field decisions that might
alter the locations for sample collection that have been selected as part of a formal strategy. Such .locations should be
representative of the variation of all characteristics of the sampled matrix that might affect asbestos release. It is
inappropriate, for example, to adjust the location of a sample just because a large rock happens to be located within
the footprint over which the sample is supposed to be collected; the presence of-that rock as part of that sample helps
to represent the fraction of the surface of the sampled matrix from which asbestos release cannot occur.
When used,to represent the central characteristics of a large matrix, random or systematic sampling schemes depend
on faithfully preserving the consequences associated with the choice of each, sampling location. In general, therefore, it
is not appropriate to alter the selected locations even if collection of a sample at a specific location is impossible.,
Rather than altering, such a location, any difficulties or interference that may hinder sample collection at a defined
location shall be noted in detail in the field log book.
8-1
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All sampling equipment shall be washed thoroughly with water and detergent between
collection of each sample. Sampling equipment shalj then be rinsed thoroughly with filtered,
distilled water and allowed to air dry. Forced air may be used to expedite drying. If forced air
is to be used to facilitate drying, however, such air must be passed through a HEPA filter to
prevent delivery of any potential contamination.
Record the identification number, the date, time, and method of collection for each sample in
a field notebook. Record the. locations from which each sample is collected in the field
notebook. Note in the logbook any changes between the sampling locations proposed in the
sampling strategy and the actual locations sampled. As indicated previously, such changes
are to be avoided to the extent possible. If changes are absolutely necessary, clearly
document the rationale behind each change.
Supplement written documentation with photographs of each sampling location. This is
particularly important if the sampling locations are not laid out on a formal, documented
sampling grid that is tied to a permanent field marker.
8.1.1 Sampling to Derive Estimates of Asbestos Concentrations in a Road
Surface
To illustrate the important features of sampling for this method, assume that sampling is to be
performed to determine the concentration of releasable asbestos in the material of a
serpentine-covered road. In this case, it is assumed that measured asbestos concentrations
are to be related to current emissions so that it is only the actual surface layer of the road
that is of interest.
Sampling a road surface shall be conducted using a metal template to define the bounds of
each sample and a trowel (or other digging device) to remove material within the template to
a uniform depth of 0.5 in. (approximately 1.5 cm). To assure that the samples collected
exceed 1 kg in mass (assuming a density for unconsolidated serpentine of 2.2 g/cm3), the
sample volume should be a minimum of 450 cm3 (28 in3). Assuming, as indicated above, that
each sample will be excavated to a uniform depth of 0.5 in., an 8 in. square hole in a 12 in.
aluminum template works well.
At each selected sampling location, center the template on the defined location and press it
firmly against the .ground surface. Carefully excavate the material within the template to a
uniform depth of 0.5 in. and place the material in a clean, pre-weighed bucket (see Section
8.2.1 )14. Transport the sample to a central location on the site where field preparation
(Section 8.2) will be performed. ,
8.1.2 Sampling a Mine Tailings Pile to Derive Estimates
Concentrations Within the Pile
of Asbestos
As a second illustration of sampling to support this method, assume that sampling is to be
performed to determine the concentration of releasable asbestos in the material of a mine
Depending on conditions encountered, it may be necessary to remove surface debris (such as leaves or foreign dust)
from an area prior to sampling. The determination as to whether or to what extent surface debris needs to be removed
prior to sampling should be based on careful inspection of the sampling location and review of the motivation for"
sampling. Surface debris should generally nof be removed unless such material is clearly distinguished visually from
the matrix material to be sampled.
8-2
-------
tailings pile. Assume further that the goal is to predict long-term emissions from the pile
based on the asbestos concentrations measured. In this case, it is the concentration of
asbestos within the volume of the entire pile that is of interest.
For the assumed tailings pile, conduct sampling using a hand auger (if the pile, is no thicker
than -a few feet) or a power auger or other drilling equipment (if the pile is significantly thicker
than a,few feet). A coring cylinder that is 12 in. long and 2 in. in diameter (assuming an
average density for 'the, pile material of 2.2 g/cm3) yields a sample of approximately 1.4 kg.
Such a cylinder shall be collected from each location (defined in 3-dimensions: longitude,
latitude, and depth) that is selected for sampling within the pile.
Cores shall be driven until their mid-point overlies the proposed sampling location. Collect
the core carefully from each selected location, being sure that the entire core is extracted
from the pile. Transport the sample to a central location on the site where field preparation
(Section 8.2) will be performed.
8.2 FIELD PREPARATION
Although the following activities might conceivably be conducted in the laboratory (following
collection and shipment of kg size samples), to minimize the mass of samples sent to the
laboratory and thereby reduce costs, the following field preparation activities are incorporated
into this method. For special cases, assuming that the laboratory of choice has access to the
required equipment in the required protective enclosures, these activities may be conducted
in the laboratory rather than in the field.
Per the instructions in the following sections, samples that are collected as defined in Section
8.1 are to be: , ._-'.'-. ... . '- .
weighed; '
sieved to separate a coarse and fine fraction;
the coarse and fine fractions are to be weighed;
the fine fraction is to be homogenized and split; and
each of the two final sub-sample splits of the .fine fraction are to be weighed,
packaged, and shipped to the laboratory (as paired duplicates).
8.2.1 Weighing .
As indicated in Section 8.1,, samples shall be'transported in clean, pre-weighed buckets'from
the locations at which they were collected to a central location for field preparation. The first
step of the process shall be to weigh each'sample.
Kg size samples are to, be weighed using a field scale capable of reading mass with a
minimum precision of ± 10 g. If necessary, wipe the outside surface of each sample bucket
with a clean, dry (asbestos free) cloth before placing it on the scale (Figure 8-1). Record the
mass measured for each sample (along with its identification number) in a field notebook and
subtract the tare weight of the bucket to derive the net weight of the sample. .
8-3
-------
FIGURE 8-1
WEIGHING A SOIL SAMPLE ON A FIELD SCALE
Bucket for
Fine Fraction
-------
Following size reduction (Section 8.2.2), both the coarse and fine fractions of each sample
are to be. weighed agajn. If necessary, wipe the outside surfaces of the buckets containing
each size fraction with a clean, dry (asbestos free) cloth before placing it on the scale..
Record the measured weight for each fraction in the field notebook under the appropriate
sample identification number. Subtract the tare weight of each bucket holding, respectively,
the coarse and fine fractions from the sample and record the net weights of each in the field
notebook.
'Following homogenization and splitting (Section 8.2.3), sub-samples that are to be sent to the
laboratory are to be weighed yet again. In this case, sample weights are expected to range
between approximately 50 and 80 g (see Section 9.1) and will need to be measured on a
scale that can achieve a precision of ± 0.2 g.. Depending on the types of equipment
available to' the sampling team, this may or may not be the same scale that is used for
weighing the initial (heavier) samples. When sending 50 to 80 g splits to the laboratory, both
halves of the final sample split shall be sent to the laboratory as a duplicate pair. ,
' r " '
Wipe the outside surface of each sample container with a clean,.dry (asbestos free) cloth
before placing it on the scale. Record the weight, identification number, and pedigree of
each sample split of each duplicate pair sent to the laboratory in the field notebook (Figure
8:2). Subtract the tare weight of each sample container from each sample and record the net
weight of each sample in the field notebook next to the appropriate sample identifier.
Package and send each sample to the laboratory as described in Section 8.4.
8.2.2 Size Reduction
After collection and the initial weighing {described above), pass each sample through a clean,
wire-mesh sieve with 1 cm (3/8th in) openings. Reduce all clods and soft aggregates by
hand and force all reducible material through the sieve into a clean, pre-weighed bucket
(Figure 8-3), Stones and debris retained by the sieve that cannot be hand crushed shall be
placed in a separate pre-weighed bucket. Once separated, the coarse and fine fractions from
each sample are to be weighed separately (Section,8.2.1).
Clean the sieve with detergent and rinse with filtered, distilled water between samples. Dry
the sieve with an asbestos free cloth or with appropriately filtered, forced air before each use.
8.2,3 Sample Homogenization and Splitting
The fine fraction of samples collected for this method may be homogenized and split by
either of two procedures.: ' .. ,
8-5
-------
FIGURE 8-2
WEIGHING A SAMPLE SPLIT ON A FIELD SCALE
Scale ,
Sample Container
-------
'\;'^li^ * ''1''<';'^:^°'"".»{*<*9J^ -,- ',/S*:*"," "r J ° \< (-xV -'""
> T %'"/^ V /'' ?' ^ * *»+ ^^ ^ "?** ^ i'Hj>0" "* ^ <' ^ * "- ^ * J ^ ^ «* > ^ < ^ \ ^Cs *v s t'^ '_, * " ' ^ < °^/ T ». " *^s *f * y* j. SI>'' ^} ^/J? , f *"" > f ** ' < '
x^ *<^>j*^ J*^ ^f (> *4j^lv A ' W*}* ^ " ?*« ^"'* '^^ * ^^ <. V \>* ^s* ^^ss cj.^.^^ , tj ^ ^ '> %" ^ .A" ^ -,^y N >J > V0< o '^'o'* ' " "^^ -~ « * / ^ v/t '<
-------
Option 1: use of a riffle splitter15. Set a clean, dry riffle splitter with 3/4 to 1.in.
chutes (Figure 8-4) on its stand on flat ground and place two receiving trays under the splitter
so that they will each catch material that falls through one of the two sets of chutes (Figure
8-5). Place the sample to be homogenized in a third splitter tray (which must be clean and
dry). Shake the splitter tray gently, until the sample is evenly distributed within the entire tray.
Place the long lip of the tray containing the sample against the inside of the long lip of the
splitter hopper and slowly rotate the tray along an access defined by its lip so that the sample
slowly empties into the splitter and slides down the near wall of the hopper to the chutes
(Figure 8-5). Continue to rotate the tray until it lies entirely inverted over the top of the
hopper of the splitter.
Tap the tray vigorously several times to free any remaining material and remove the emptied
tray from the splitter. Tap the splitter vigorously several times to facilitate the flow of all
material through the chutes into the receiving trays. If necessary, any sample remaining
along any of the soldered corners and nooks of the splitter may be freed with a clean, coarse
nylon brush. When brushing is completed, tap the brush vigorously against the splitter wall
to free any material clinging to the brush . . Remove the two receiving trays (each
containing-half of the sample) from the splitter.
What is to be done next depends on whether the goal is to homogenize the sample or to split
the sample. If the sample is in the process of being homogenized, combine the half of the
sample from each receiving tray back into the third tray from the splitter. Be sure to tap each
tray vigorously to assure quantitative transfer of the sample material. Replace the two empty
receiving trays under the splitter and repeat the process of splitting the sample (in the manner
described above). The sample should be subjected to a minimum of five cycles to assure
adequate homogenization.
If the goal is to split (rather than homogenize) the sample, pour the material in one of the
receiving trays from the'splitter into a spare bucket and tap the tray vigorously to assure
quantitative transfer. The remaining tray that still contains sample material now becomes the
new sample tray and the original sample tray (now empty), along with the just emptied
receiving tray, should be placed under the splitter as the new receiving trays.
Repeat the process of dispersing the remaining sample material (containing half the mass of
the original sample) by shaking the sample tray so that it is uniformly distributed. Repeat the
procedure described above for splitting the sample, discarding the material in one of the two
receiving trays each time, until the mass.of the material in each receiving tray at the end of
one cycle falls in the range of 50 to 80 g. At that point, carefully transfer the material from
15
16
Results obtained as part of the pilot study for this method (Berman and Kolk 1994) suggest that some respirable dust
may be lost each time a sample is passed through a riffle splitter. If the process is conducted carefully, however, such
loss may be kept sufficiently small so that the multiple passes required to homogenize and split a sample properly will
not significantly alter the estimated concentration of dust and asbestos derived using this method; losses should be" less
than an absolute maximum of 10 to 15% of the total respirable dust in the sample after as many as 10 passes. Because
the estimate of the magnitude of loss was necessarily based on measurements of samples that had to be suspended in
water, however, actual losses for most cases are expected to be much smaller.
One important consideration: avoid using the splitter in the field on windy days (i.e. when wind velocities exceed
approximately 5 mph) unless an effective wind screen can be devised.
The brush will have to be washed, rinsed, and dried thoroughly before use on another sample.
. 8-8
-------
-------
FIGURE 8-5
USING A RIFFLE SPLITTER TO HOMOGENIZE/SPLIT SAMPLES
,, t ' - x - >
JJ* ,*s' i **»"" * *.
^«,«»,-'*', cf*t^>Hf fe.«
; *'. Aj-.^-lifTs ' a?.. V WC^^^M^^ *%^>i
SaropteTray' Receiving Trays Splitter Hopper 'Splitter Stand
-------
each tray into a clean, pre-weighed sample bottle (Figure 8-6) to be^weighed (Section 8.2.1)
and packaged for shipment to the laboratory (Section 8.4). Be sure that samples are
transferred quantitatively from each tray. h "
NOTE
NEVER MAKE A PARTIAL TRANSFER OF MATERIAL FROM A SPLITTER TRAY TO
A RECEIVING CONTAINER. THIS WOULD, J3EFEAT THE PURPOSE FOR
HOMOGENIZATION AND SPLITTING BECAUSE IT IS IMPOSSIBLE TO ASSURE
THAT ALL OF THE SIZE COMPONENTS OF THE SAMPLE ARE TRANSFERRED
PROPORTIONALLY UNDER SUCH CIRCUMSTANCES.
Clean the body of the spijtter, all trays, and any appurtenant equipment (such as a nylon
brush) between samples (but not between splits of the same sample) with a detergent wash
followed by thorough rinsing with distilled, filtered water. Be sure that the splitter, trays, and
appurtenant equipment are completely dry before use. These may ,be dried with forced air
that is properly filtered to be free of asbestos. ,
Option 2: Use of a mixer with coning and quartering. Samples may also be
homogenized for this method using any of various sealed, rotating mixers (tumblers). The
mixers should contain internal.baffles to promote mixing. Such mixers must be sufficiently
large to accommodate the largest sample to be homogenized17 with adequate room to
spare so that tumbling is facilitated. The mixers must be sealable to prevent the loss of fines
during mixing. v
Place the fine fraction of the sample to be homogenized in a clean, dry mixer. Seal the mixer.
Tumble the mixer at the manufacturers recommended speed for an amount of time
recommended by the manufacturer to assure adequate homogenization. Stop the mjxer and
allow ample time (approximately 15 minutes) for the fines to settle. Disconnect the mixing
container from the rest of the mixer. Open the mixer.
Under this option, a procedure termed coning and quartering is used to split a homogenized
sample. Lay out a clean, aluminum plate on a flat surface. Hold the mixer immediately over
the center of the plat? and rotate the mixer around an axis represented by the lip on one side
.of its mouth so that the sample material slowly pours onto the metal plate forming a
symmetrical cone (Figure 8-7). Keep the point at which the poured material impacts the cone
at the same spot and slowly'raise the mixer as the pouring continues to keep the distance
between the mixer lip and the top of the cone, approximately constant. When the mixer is
fully inverted, tap it vigorously to complete the quantitative transfer. . -,
To halve the cone, hold a second (clean, dry) aluminum plate directly over the apex (top
center) of the cone at an angle that is perpendicular to the aluminum plate on which the cone.
lies. Slowly lower the second plate so .that it splits the cone precisely in half (Figure 8-8a).
While holding the two plates steady, push one half of trie cone off of the original plate and
away from the rest of the sample (Figure 8-8b). Brush the area from which this material is
If samples are to be composited as described in Section 8.3, the mixer may have to be capable of handling samples
that range up 40 kg in size.
''" - / ' 8-11
-------
FIGURE 8-6
LOADING A SAMPLE SPLIT INTO A SAMPLE BOTTLE
Scale
Bottle > -Receiving Trays '- Rittte Splitter1 x-
,T ~* » Frorp>Splitter - " <* "
-------
FIGURE 8-7
TRANSFERING SAMPLE FROM A MIXER TO A PLATE
FOR CONING AND QUARTERING
Mixer
Slowly
Increase
Tilt
Keep This Distance Small
and Constant
-------
FIGURE 8-8
CONING AND QUARTERING
Slow 1
Steady 1
Motion
Aluminum" Plates
A. POSITION OF ALUMINUM PLATES IN PREPRATION FOR HALVING SAMPLE
Remove All Material
From This Side of
Vertical Plate
B. POSITION OF ALUMINUM PLATES AFTER HALVING SAMPLE
-------
removed to complete a quantitative transfer, leaving only clean metal. Once half of the
sample material has been removed, withdraw the vertical aluminum plate slowly by pulling it
upward vertically.
To complete'quartering of the cone, rotate the vertical aluminum plate above the cone 90° on
a vertical axis. Lower the plate slowly once again so that it splits the remaining portion of the
sample cone-evenly into two new halves. Once again, quantitatively remove half of the
sample material (i.e. remove all of the material from one side of the vertical plate). This
process may be repeated by quantitatively transferring the remaining sample material into a
clean bucket and pouring the sample onto the clean aluminum plate to form a new cone.
Repeat the coning and quartering process until the remaining quarters (or halves) of the
sample at the end of one cycle falls in the range of 50 to 80 g. At that point, carefully transfer
the materialfrom each quarter (or half) into a clean, pre-weighed sample bottle to be weighed
(Section 8.2.1) and packaged for, shipment to the laboratory (Section 8.4).
NOTE
NEVER MAKE A PARTIAL TRANSFER OF MATERIAL FROM ANY PORTION OF
THE CONE THAT DOES NOT INCLUDE A WEDGED-SHAPE SLICE THROUGH THE
CENTER OF THE CONE OVER ITS ENTIRE THICKNESS (DEPTH). THIS WOULD
DEFEAT THE PURPOSE FOR FORMAL CONING AND QUARTERING BECAUSE IT
IS IMPOSSIBLE TO ASSURE THAT ALL OF THE SIZE COMPONENTS, WHICH
WILL WOT BE HOMOGENEOUSLY DISTRIBUTED VERTICALLY THROUGHOUT THE
CONE OF THE SAMPLE, ARE TRANSFERRED PROPORTIONALLY.
8.3 COMPOSITING SAMPLES (OPTIONAL)
In many cases, there may be interest in limiting the number of analyses required to
characterize a matrix that serves as a potential source without sacrificing representativeness.
One procedure that may be employed for this purpose is to composite samples in the field.
Note however, while compositing can reduce the cost of analysis by reducing the number of
samples requiring analysis, also lost is information concerning the spatial variability of the
sampled matrix. Therefore,.' if such information is desired for any particular reason,
compositing is not recommended. -
Only minor adjustments to the field preparation procedures described above are required to
incorporate compositing into this method. First, during planning, group the samples to be
collected in the field into sets that are to be composited. For example, there may be a desire
to combine all samples from the eastern part of a road into a composite representing trie east
end of the road. Similarly, samples from the west end might be combined into a west end
composite. Alternately, all samples from the road may be combined into a.single composite,
representing the road as a whole. As another alternative, the composite road sample might
also be split into duplicate pairs to allow determination the variability contributed by sample
preparation and analysis: Such decisions shall all be determined during planning.
8-15
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NOTE
It is expected that the same set of locations will be selected for sample collection
whether or not compositing is employed; compositing only changes the number of
analyses required. This is because, the same number of samples collected from a set
of locations selected using the same formal procedures are still required to adequately
characterize the sampled matrix, whether or not samples are composited prior to
analysis.
When brought to the central location where field preparation is conducted, after the initial
weighing, the samples collected from a set that is to be composited can be combined in a
common bucket. Modify the procedures described in Sections 8.2.1 and 8.2.2 as follows:
transport each sample (of a set to be composited) from the point of collection to
a central location in a clean bucket;
weigh the sample and record the weight along with the appropriate sample
identifier. Subtract the tare weight of the bucket and record the net weight of the
sample;
sieve the sample and collect the fine fraction from each sample in the set to be
composited in a common bucket. Weigh the bucket containing the fines
following the addition of the contributions of each sample and subtract the
previous weight of the bucket to determine the net weight contributed by each
sample. Record the weight with the proper identifier in the field notebook; and
transfer the coarse fraction from each sample in the set to be composited to a
common bucket. Weigh the bucket containing the coarse fraction following the
addition of the contributions from each sample and subtract the previous weight
of the bucket to determine the net weight contributed by each sample. Record
the weight of the coarse fraction with the proper sample identifier in the field
notebook.
Once all the samples of the set to be composited have been collected and added, the
combined fine fraction from all of the samples (which resides in a common bucket) shall be
given a separate identifier representing the intended composite. Record the new identifier in
the field notebook. This material can now be treated as a single, composite sample for all
remaining steps of field preparation and sample handling, packaging, and shipment to the
laboratory. Thus, homogenize and split the sample as described in Section 8.2.3 and
package and ship the sample to the laboratory as described in Section 8.4. Record the
appropriate weights of the samples to be shipped as described in Section 8.2.1.
8.4 SAMPLE HANDLING AND SHIPMENT
Once their weights and identifiers are recorded, the samples to be shipped to the laboratory
must be sealed and labeled. Fill out and apply appropriate labels to each sample bottle.
Record the date and time that each sample was created on .both the label and the field
notebook and be sure that the identification numbers on the label and field notebook match.
8-16
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Fill out the appropriate chain of custody forms and seal each-sample cap with a breakaway
label, .As indicated in Section 12.2, be sure to complete the field activities report and to
include this report in the package with samples sent to the laboratory.
Wipe each sample to be shipped to the"laboratory with a clean, asbestos-free cloth and place
it in a cooler. 'Ship samples to the laboratory in a cooler with ice to limit biological growth
during shipment. Sufficient ice must be provided to assure that samples remain cold until
received and processed by the laboratory. . '
NOTE
When matrices that are sampled contain a significant fraction of.coarse material (i.e.
more than 10% by mass), the final determination of the concentration of asbestos in
that matrix must be adjusted to account for the fraction of coarse material./ This
requires determining the ratio of the mass of fine material in the sampled matrix to the
total mass of material in the sampled matrix to generate a "coarseness adjustment
factor". The concentration of asbestos determined for samples sent to the laboratory
must .then be multiplied by this coarseness adjustment factor to determine the
concentration of. asbestos in the sampled matrix.
" . '- *(' '
Equations for deriving and using the coarseness adjustment factor, are provided in
Section; 11.4.3. The weights of the coarse and fine fractions of each sample are to be
included (along with the appropriate sample identifiers) as part of the field activities
report that is to be shipped, with the sample to the laboratory (Section 12.2). This
assures that individuals responsible for estimating the concentration of asbestos for
the project have access to the required field information.
8-17
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-------
9.0 SAMPLE PREPARATION BY DUST GENERATION
The primary purpose for sample preparation by dust generation that is described in this
section is to generate dust-laden filters that can be suitably prepared for analysis by an
appropriate method for the determination of asbestos in air8. The rate of generation of
.total respirable dust is also monitored and is used- both to estimate the total mass of
respirable dust in the original sample and to tie asbestos structure concentrations determined
from filters-to the mass of the original sample. Such information might also be used in some
studies to characterize the releasibility of asbestos (or total dust) from particular sample
types. '
A detailed description of the apparatus employed for dust generation and its theory of
operation is provided in Appendix A. Specifications., and construction drawings are also
provided.
9.1 SAMPLE RECEIVING AND STORAGE
I , ' '.-"< ' "
All samples received from the field are to be wiped Clean with a damp cloth prior to storage
or other handling. Samples shall be stored at ice temperature (to minimize biological growth)
until sample preparation is initiated. To minimize complications from biological'agents, once
initiated, sample preparation shall be completed expeditiously. In any case, sample
preparation shall be completed within 48 hours.
Samples to be prepared using the dust generator are to be inspected for the presence of free
water. If a sample contains free water or if the sample appears visibly moist, it shall be dried
at low temperature. If time permits, place the sample in an open, shallow container and store
it for several days in a desiccator containing moist potassium carbonate dihydrate or another
salt that corresponds to the salt selected for humidity control (see Section 9.3.2). The type of
salt placed in the desiccator is chosen deliberately; rather than to dry the sample completely,
the goal is to bring the moisture content of the sample into equilibrium with conditions that
Will prevail in the dust generator.
If sufficient time is not available to dry the sample in a desiccator, the sample may be oven
dried. Dry the sample in an open, shallow container in an oven that is maintained at a
temperature .below 60° C until the sample comes to constant weight. Note that oven-dried
samples may require additional time for conditioning (Section 9.4.2) because the moisture"
content of the sample will need to be increased to bring it into equilibrium with conditions
prevailing in the dust generator.
Once dry, samples smaller than 80 g can be loaded directly into the tumbler of the dust
generator (Section 9.4.1). Larger samples must be homogenized and split, as described in
Section 9.2, prior to being placed in the tumbler of the dust generator.
18
The ISO method for the determination of asbestos in air (using either an .indirect or a. direct filter preparation technique -
- Chatfield 1993) is the default method recommended for use in tandem with this method.
'".''- . - ' 9-1 -
-------
9.2 SAMPLE HOMOGENIZATION AND SPLITTING IN THE LABORATORY
Samples received from the field that are larger than approximately 80 g must be dried, as
described above, and then homogenized and split as described in this section.
WARNING:
BECAUSE ASBESTOS CONTAINING DUSTS MAY BE GENERATED FROM THE
HANDLING AND PREPARATION OF BULK SAMPLES, ALL OF THE FOLLOWING
PREPARATION STEPS SHALL BE PERFORMED IN A PROTECTIVE ENCLOSURE
(I.E. A HEPA FILTERED GLOVE BOX OR AN APPROVED FUME HOOD THAT IS
DESIGNED TO MINIMIZE EXPOSURE TO LABORATORY PERSONNEL19). IT IS
ALSO NECESSARY THAT ALL HANDLING OF BULK SAMPLES BE CONDUCTED IN
A SEPARATE ROOM THAT IS PHYSICALLY ISOLATED FROM THE ROOM(S) IN
WHICH AIR SAMPLES ARE HANDLED AND ASBESTOS ANALYSIS IS
PERFORMED.
As with field homogenization and splitting (Section 8.2.3), either of two options may be
selected for homogenization and splitting in the laboratory. When performed in the
laboratory, however, such equipment must fit within an appropriately designed, protective
enclosure, which is why field preparation may.be cost-effective.
Homogenize large samples in precisely the same manner as described in Section 8.2.3.
Once samples are homogenized, split samples in precisely the same manner as described in
Section 8.2.3. Continue splitting until a paired set of samples are produced that each contain
between 50 and 80 g of material. Record in a laboratory notebook'the final weights and
identifipation numbers of the samples homogenized and split.
9.3 DUST GENERATOR SETUP
Prior to using the dust generator, a supply of at least 35 MCE filters must be conditioned and
stored .for use, the constant humidity chamber must be loaded with the appropriate solution,
the scrubber must be primed, and air flow within the dust generator must be calibrated and
adjusted.
. 9.3.1 Conditioning a Stock of Filters
A stock of at least 35 filters (0.45 jim pore size, 25 mm diameter), all from the same filter'lot,
must be conditioned in a desiccator overnight to bring them into equilibrium with the relative
humidity at which they will be used during a run. Place the 35 MCE filters in a desiccator
containing moist salt of the same variety as that selected to fill the pans in the humidity
control chamber of the dust generator (Section 9.3.2). For most applications, this will be
potassium carbonate dihydrate (see Appendix A).
The work should be performed in a Class II biohazard hood as per the specifications of Standard #49 of the National
Sanitation Foundation. ,
9-2
-------
After storing the filters overnight in the desiccator, pre-wejgh each filter to a minimum
precision of ±0.0002 g20. Each filter shall then be placed in a separate, covered Petri dish
with its weight marked on the top of the container. The lids shall also be numbered
sequentially and the filters shall all be used during the run in the order numbered.
9.3.2 Initiating Humidity Control
Use asbestos-free (filtered, distilled) water to make a 2 L solution of saturated salt. As
indicated previously, for most applications, use potassium carbonate dihydrate (to achieve a
relative humidity of 43%), but other salts may be used for specific applications (see Appendix
A)21. , -
Prepare the solutions by placing 1000 g of the anhydrous salt into a one L container and
adding distilled water to fill the container. The container should be capped and additional
water and salt added as necessary the next day. No water or salt should be added within a
day of using the mixture since some time is needed to saturate the salt solution and form a
hydrate when adding anhydrous potassium carbonate. However, sufficient salt shall have_
been added previously to assure that sufficient undissolved potassium carbonate dihydrate""
has precipitated in the container to form a closely spaced layer of the material on the bottom
of the shallow pans that will be covered with a thin layer of the solution (next paragraph).
.Open the top of the humidity control chamber and remove the two pans. Fill each pan with
the saturated salt solution being sure that a small quantity of excess (undissolved) salt is also
transferred to each pan. Replace the pans and seal the top of the plastic enclosure; air
should enter the enclosure primarily from the front opening.
9.3.3 Priming the Scrubber
Fill the round bottom flask of the scrubber to about one third full with asbestos-free (i.e.
filtered, distilled) water. Initiate the flow of ice water through the entrance and exit
condensers. Adjust the variable voltage transformer on the heating mantle so that water in
the round bottom flask boils and the rate at which condensate drops back into the flask from
the condensers is approximately equal to one drop per second.
9.3.4 Adjusting Initial Air Flow
The air flow within the various components of the dust generator must be adjusted so that""
flow within the vertical elutriator will properly separate and pass only respirable particles.
Based on the discussion presented in Appendix A (Section A.2.3), tire proper linear flow rate
in the elutriator shall be set at 0.31 cm/s, which is 5% greater than the Stokes' velocity.
estimated for the largest spherical, respirable particles (i.e. those with a radius of 5
20
21
Fitters to be used to collect samples over the isokinetic sampling tube of the elutriator (see Section 9.4.5) must be
weighed to a minimum precision of ± 0.00002 g.'
Note that potassium carbonate dihydrate is not the usual form of potassium carbonate sold commercially. The usual
commercial forms are the anhydrous and the sesquihydrate. The dihydrate can be made by allowing either of the com-
mercial varieties of the salt to stand in their saturated solution for some extended period of time with some temperature
cycling (Berman and Kolk 1994). A week appears to be sufficient but the process can be accelerated by augmenting
the temperature cycling. . ' : >
..-..'..''. .-9-3 '-..'- '''
-------
Next, calculate the required volumetric air flow, Vv, within the elutriator using Equation 9-1:
= 81.1*V
(9-1)
where:
V, is the estimated linear flow rate required to separate respirable
particles (i.e. 0.31 cm/s); and
Vv is the corresponding volumetric flow rate (cm3/s) through the
elutriator.
The coefficient, 81.1, in Equation 9-1 corresponds to the cross-sectional area of the elutriator
(in cm2).
To adjust the initial flow valve settings on the pumps, first connect one of the flowmeters such
that air flows directly from the exit opening at the top of the elutriator that is not articulated
with the isokinetic sampling tube22. This is the exit that opens directly into the top, tapering
portion of the elutriator (see Appendix A) and is labeled the "ME" opening in Figure A-1. A
filter cassette containing a filter from the batch of filters to be used for the run shall be placed
between the flowmeter and the pump when adjusting the flow valve on 'this pump.
NOTE
The easiest way to directly connect a flow line to one of the top openings of the
elutriator (the ME or the 1ST opening) is to align the appropriate slide mechanism so
that a filter mount is directly over the opening, mount a cassette without a filter into the
mount, and connect the air flow line to the exit side of the filterless cassette (see
Section A.I,6 of Appendix A). During calibration, such a line would then feed
sequentially into a flowmeter, a filter-containing cassette, and a pump.
Connect a second flowmeter directly to the exit line of the scrubber (the entrance line of
which should already be attached to the two side exit openings on the elutriator) and place a
filter cassette containing a filter from the batch of filters to be used for the run between this
flowmeter and the pump for the scrubber. -
Adjust the flow control valves on both the scrubber pump and the pump to be connected to
the ME opening of the elutriator so that flow in both lines are equal and that each flow is set
at0.48*Vv.
Connect a third flowmeter to the exit openi'ng on the top of the elutriator that articulates with
the isokinetic sampling tube. This is labeled the "1ST1 opening in Figure A-1.
22
To access this opening, it will be necessary to dismount any filter cassettes from the appropriate slide mechanism and
to align one of the two openings in the appropriate slide mechanism over the desired opening in the elutriator (see
Appendix A).
9-4 '
-------
The flowmeter attached to the 1ST opening shall also be backed by a filter cassette containing
a filter from the batch to be used during the run and adjust the flow in this line so that it is
equaj to 0.047*VV23. Due to the low flow required on this Jine, an auxiliary low flow valve is
also attached to this pump and must be adjusted to achieve the desired flow. To optimize
conditions, it may be necessary to adjust the flow control valves on the three air lines that exit
the elutriator iteratively.
To prepare for a run using'the dust generator, disconnect the flowmeters from the slide
mechanisms over the top bpenings of the elutriator (I.e. the ME and 1ST openings) and mount
filters in each of the four cassette holders on the two slide mechanisms that cover the two
elutriator openings. Connect one of the air flow lines coming off of the 'T1 from each pump to
each of the two filters on the same slide mechanism for the appropriate opening of the
elutriator (i.e. the opening for which the pump had been calibrated). Then adjust each slide
so that one filter cassette is aligned directly over each elutriator opening. Be sure that the
valves on each 'T1 are configured so that flow is directed from the filter cassette that is
aligned directly over the elutriator opening (see Section A.1.6 of Appendix A).
NOTE
The connections between the exit side of the filter cassettes mounted on the slide
mechanisms and the flow control valves on the pumps should now be direct; there
should be no^second filter cassette in the line.
The flowmeter attached to the exit line of the scrubber may remain attached during a run to
monitor air flow through the scrubber. If there is a desire also to monitor airflow through one
or both of the filter cassettes mounted over the top openings of the elutriator during a run,
flowmeters may now be attached to the downstream side of the filter cassettes (i.e. between
the filter cassettes and the pumps). Due to the pressure drop across the filters, however, the
readings from these flowmeters must be adjusted using the following equation to provide
estimates of the true flow through each elutriator opening:
Ft =
(9-2)
where:
Ft is the true flow rate through the elutriator opening (cm/s);
Rf is the flow reading from the flowmeter (cm/s);
Pf is the pressure at the flowmeter (torr);
Tf is the absolute temperature at the flowmeter (°K);
23
The coefficient, 0.047, used to estimate the volumetric flow rate for air passing through the isokinetic sampler represents
the fraction of the cross-sectional area of the elutriator that is subtended' by the isokinetic sampling tube and therefore
represents the fraction of the total flow that should pass through the tube, assuming that flow in the elutriator has been
properly set. , .
9-5 . - "'':
-------
Pt is the pressure at the elutriator opening (torr); and
Tt is the absolute temperature at the elutriator opening (°K). .
To use this equation, Pf and Pt will have to have been measured during flow calibration, prior
to a run, using mercury manometers or other appropriate pressure measuring devices.
Generally, Tt and Tf can be considered equal and will drop out of the equation. However,
Equation 9-2 can also be used to adjust .flow readings between calibrations and runs that are
conducted on different days, such that temperatures may vary between the time during which
the calibration was conducted and the time that the run is performed.24
9.4 DUST GENERATOR OPERATION
To prepare asbestos samples using the dust generator, load the tumbler, condition the bulk
sample, begin the run, monitor the rate of dust generation, and collect appropriately loaded
filters for asbestos analysis. Asbestos is also collected in the scrubber. Prior to use, be sure
that the dust generator is clean (see Section 9.5). . ,
9.4.1 ' Loading the Tumbler
Detach the tumbler from its drive motor and the vertical elutriator and remove it from the
plastic enclosure at the bottom of the dust generator (see Appendix A). Place the tumbler on
a flat surface and open the top for loading. Be sure that the tumbler is clean prior to loading.
Introduce a sample25 by holding the sample container against the inner lip of the tumbler
and tilting the container so that the sample pours smoothly into the tumbler. ' Move the
sample container back and forth along the length of the tumbler to facilitate uniform
deposition of the sample in the tumbler. When pouring is complete, tap the sample container
vigorously so that the quantitative transfer is complete. The masses of samples introduced
into the tumbler shall range between 50 and 80 g. Larger samples shall be homogenized and
split prior to loading as described in Section 9.2.
Shake the tumbler gently to assure uniform deposition of the sample within the tumbler, which
should be no more than about one third full. Be sure that the rubber gasket on the tumbler is
in good repair and properly seated. Replace the gasket if it is worn. Secure the top of the
tumbler with 10 screws and replace the tumbler within the plastic enclosure at the bottom of
the dust generator. Reattach the elutriator entrance tube and D.C. motor to the tumbler (see
Appendix A). ,
24 Because the viscosity of air is somewhat temperature dependent, when runs are to be conducted at temperatures that
differ by more than a few degrees from room temperature (nominally 20° C), Equation A.10 (in Appendix A) may have
to be adjusted to account for the varying viscosity (see Equation A.9) so that the correct flow regime can be established
at the new temperature to assure that the elutriator of the dust generator passes only respirable particles. .
25 Samples to be introduced into the tumbler shall have been dried per Section 9.1.
9-6
-------
9.4.2 Conditioning the Sample >
Before conditioning the sample, be sure that the dust generator has been properly set up.
This means, check that: , .
the pans in the constant humidity chamber have been filled with saturated
solution;
filters have been mounted on each of the four cassette mounts on the slide
mechanisms atop the elutriator;
water is boiling in the scrubber; >
the air flow valves have been properly set; and
all air lines between the dust generator, flow valves, and pumps are properly
configured (see Section A.1.6 of Appendix A).
To condition the sample, turn on all pumps and begin the flow of air through the dust
generator. DO NOT TURN ON THE TUMBLER MOTOR. Allow the flow of air to continue for
a minimum of two hours before beginning a run. If the sample was oven dried rather than
equilibrated with,an appropriate salt in a desiccator (Section 9.1), the sample should be
conditioned for a minimum of four hours prior to initiating a run.
9.4.3 Initiating a Run
Once the sample has been conditioned, set the tumbler drive motor to 30 rpm and turn it on.
Simultaneously, move the two slide mechanisms at the top of the elutriator so that new, clean
filters are now aligned over both the ME and ,'l'ST openings of the elutriator. Be sure to
change the valve orientations on. the lines leading to the filters so that air flow is directed
through the filter cassettes that are newly aligned with the elutriator openings.
Replace the filters originally aligned over the elutriator openings (but no longer aligned) with
clean, filters and weigh and store the old filters in labelled Petri dishes. These filters are
equipment blanks. After five minutes,26 move the sliding mechanism again to bring new,
clean filters over the ME and 1ST openings of the .elutriator. Immediately after the filters are
brought out of alignment, dismount the cassette and turn the potentially, dust-laden side of-
the filter face up before halting the flow of air through the filter (by turning the appropriate
valves). Once flow from the dismounted cassettes has been halted (correspondingly, flow will
have been re-directed to the cassettes that are currently aligned over the elutriator openings),
replace the dismounted filters with clean filters and weigh and store the dismounted filters in
labelled Petri dishes. These filters are run blanks.
As the run proceeds, record the times that air flow was started and stopped for each filter, the
initial and final weights of each filter, and the identifier of each filter in a log book. ,
26
This-interva! is selected because, in the absence of channeling, five minutes is just less than the time over which the
fastest particles are expected to reach the fitter.
' '-.-'': 9-7 '- '.
-------
9.4.4 Monitoring the Rate of Respirable Dust Generation
The rate of respirable dust generation is monitored during a run by recording the weights of a
set of filters that are sequentially changed out of the filter mounts over the ME opening of the
elutriator at defined, regular intervals. -
Initially, change the filter that is aligned over the ME opening of the elutriator at intervals of
five to eight minutes. The change is accomplished by moving the slide mechanism to switch
a new filter into alignment at the same time that the old filter is switched out of alignment.
Immediately after the filter is brought out of alignment, dismount the cassette and turn the
dust-laden side of the filter face up before halting the flow of air through this filter (i.e. by
turning the appropriate valves to re-direct air flow to the filter that is newly aligned over the
ME opening). Exchange the old filter for a new filter.
NOTE
Because the time during which air flow is directed through a dismounted cassette
(rather than the filter that is aligned over the elutriator opening) results in a disturbance
in the otherwise smooth flow of air through the elutriator, the changing of filters shall
be performed expeditiously. As long as this interval is not more than a few seconds,
however, studies indicate that this effect is not significant (Berrnan and Kplk 1994).
Along with the proper identifier, record the times during which air flow is started and halted for
each filter. Weigh each filter after dismounting. Record the initial and final weights of the filter
and the net weight of dust deposited on the filter (i.e. the difference between the initial and
final weight). ,
After exchange of the first two or three filters, the interval over which dust is collected on each
filter may be optimized. The ideal weight of dust to be deposited on each filter is between
0.01 and 0.03 g (Berman and Kolk 1994). Based on the rate of dust deposition on the first
two or three filters, estimate the interval of time required to deposit approximately 0.02 g and
exchange later filters at this rate (see Section A.2.2 of Appendix A, Equation A-8)27.
However, it is important that time be adjusted so that no more than 0.03 g be deposited on
each filter because the possibility that a portion of the deposit accidently drops from the filter
increases as the weight of the deposit on the filter increases. -
NOTE
Until there is a need for generating filters for asbestos analysis (see Section 9.4.5), the
filters that get aligned over the 1ST opening of the elutriator need to be changed only
one fifth to one tenth as often as the filters over the ME opening of the elutriator.
These filters shall be changed at this lower rate, however, to prevent the potential for a
heavy deposit to drop off of the filter and fall back into the elutriator.
At the beginning of a run the rate of dust deposition on the filters has been observed to be nearly constant with time.
9-8
-------
Continue the run at 30 rpm (with continuing exchange of filters) for approximately two .hours;
this time interval has generally been observed as sufficient to define the rate of respirable
particle rejease at this rotation rate (Berman et al 1994a). Generally, the plot of the release of
respirable dust versus time at 30 rpm shows almost no curvature (see Section 11.2).
After completing the run at 30 rpm, select a new, higher rotation rate to continue the run.
Generally, the new rotation rate selected shall be 60 rpm, unless the rate of release at 30 rpm
was noticeably low in comparison with prior runs on other samples, in .which case 90 or
120 rpm shall be used. " ' ..'.:'
NOTE
Use of the highest rotation rates should generally be avoided, unless there is
compelling evidence for their efficacy, because they tend to facilitate the transport of
non-respirable particles from the tumbler into the Bottom of the elutriator and, if such
transport is heavy, this may affect results (see Section A.1.3 of Appendix A). .
Continue the run at the higher rate of rotation by collecting a minimum of eight additional
dust-laden filters. The same procedures outlined above should be continued for collecting
data during the run at this higher rotation rate except that the interval between the exchange
of filters must be adjusted downward to assure that deposits on these latter filters' do not
exceed 0.03 g (see Section A.2.2 of Appendix A, Equation A-8, but note that the rate
constant, k, is dependent on the rotation rate for the tumbler so that Equation A-8 cannot be
extrapolated across runs).
-, ' ' ' '" '
When the run is complete, turn off the tumbler motor but allow the air flow to continue for ten
or fifteen additional minutes to empty the elutriator. Be sure to continue the exchange of
filters, if necessary to prevent overloading. The air flow pumps may now be shut off.
9.4.5 Generating Appropriately Loaded Filters for Asbestos Analysis
The, primary purpose for collecting dust on filters mounted over the exit of the isokinetic
sampling tube of the elutriator (the opening labeled "1ST1 in Figure A-1) is to obtain samples
suitable for asbestos analysis using a direct transfer technique, although use of an indirect
transfer technique is riot precluded. This is an option built into the design of the dust
generator as an alternative to preparation of a specimen for asbestos analysis using the liquid"
from the scrubber, which necessarily mimics an indirect transfer technique because (in the
scrubber) the asbestos is captured and suspended in water.
Collect filters for asbestos analysis near the end of each of the two runs (i.e. one run at each
of two rotational speeds for the tumbler) that is described in the previous section of this
chapter. Filters to be used for asbestos analysis shall be collected at the end of the runs
both because this will be the period when the rate of asbestos emission is the lowest and
because sufficient time will have elapsed over each run to allow a steady-state distribution of
particle sizes to have developed in the dust traversing the elutriator. At the beginning of a
run, only the smallest (fastest) respirable particles reach the filters and it. takes time for the
larger (slower) respirable particles in the air stream to begin reaching the filters in numbers
that are proportional to, their rate of emission from the tumbler. It takes several tens of
minutes for transport of a steady state distribution to develop.
9-9
-------
Collect multiple filters during each run that bracket the estimated time during which an
optimal loading for analysis of a directly prepared specimen is expected to be achieved.
Mount, exchange, dismount, weigh, record, and store filters precisely in the manner described
in Section.9.4.4.
Estimate the time required for achieving an optimum loading as follows. The optimal mass
loading on a filter to be prepared by a direct transfer technique lies between 1 and 10 jig
(see, for example, Berman and Chatfield 1990). Assume a target of 5 \ig. However, this may
have to be adjusted based on experience with the dust generator. Equation A-7 (Appendix A)
can then be re-arranged to estimate the time required to collect 5 fig (or some other defined
mass) of dust:
At = AM/0.047*k*Ms
(9-3)
where:
Ms is the mass of respirable dust remaining in the sample at time "t" after
the beginning of the run, but, it is assumed constant over the short
interval of time "At" (g);
AMfis the mass of respirable dust collected on a filter over the 1ST opening
during the short time interval "At" (as indicated above, assume a target of
5 jig orSxIO^g);
At is -a short time interval (no more than several minutes) during which the
release of dust is being estimated (s); and
k is the first-order rate constant for the release that is derived from the
dust measurements collected during the run (s"1).
The mass of respirable dust remaining in the sample during the time interval of interest (Kg) is
estimated using a rearrangement to Equation A-2 (Appendix A):
Ms = M *exp(-kt)
(9-4)
where:
. Ms is the mass of respirable dust remaining in the sample at time T (g);
M0 is the mass of respirable dust in the sample at the start of the run (i.e. at
time t = 0) (g).
t is the time from the start of the run to the beginning of the time interval
"At" (s); and .
k is the first-order rate constant for the release (s"1).
9-10
-------
Based on the recently completed pilot study for this method (Berman et al. 1994a), a typical
rate constant for dust emission from the tumbler is 0.004 min (6.7 x 10"5 s~1). Results from
this study also suggest that the range in respirable dust content likely to be encountered for
samples .typically run using the dust generator may vary between 0.5% and 2%. Therefore,
given a typical sample mass of 70 g, M0 for the 30 rpm run likely ranges between
approximately 0.17 and 0:68 g. Given that a typical 3D rpm run lasts for approximately
3 hours (1.1 x 104 s) and substituting these values for M0, k, and t into Equation 9-4, and
then substituting the subsequent estimate of Ms into Equation 9-3, it appears that between
2.3 and 9 seconds would be required at the end of the 30 rpm run to collect 5 jig of material
o'n a filter loaded over the isokinetic sampler.
Similarly, assuming that the initial mass of respirable dust in a sample at the beginning of a
60 rpm run, MO^Q, is equal to the remaining mass at the end of the 30 rpm run (i.e. the "Ms"
calculated above), remembering that a 60 rpm run typically lasts 2 hours (7.2 x-103 s), and
once again noting the typical value for k indicated above, Equation 9-4 is used to estimate an
appropriate Ms for the end of a 60 rpm run. Substituting this new value into Equation 9-3, it
appears that between 4 and 15 seconds may be required to collect 5^g of material on a filter
that is loaded over the isokinetic sampler at the end of a 60 rpm run.
Given the above, to properly bracket the optimal loading for a filter to be employed' for
asbestos analysis using a (direct transfer technique), collect filters over the 1ST opening of the
elutriator that are exposed for periods of 3, 10, and 20 seconds (at both the end of the
30 rpm run and the end of the 60 rpm run).
9.4.6 Obtaining Asbestos Samples from the Scrubber
At the end of all runs for a particular sample (after all pumps have been shut off), turn off the
heating mantle to the scrubber and let it cool for 10 to 15 minutes before discontinuing the
flow of ice water to the condensers. Disconnect the outlet lines from the elutriator to the
scrubber at the elutriator. Samples shall be extracted from the scrubber expeditiously to
minimize losses to the walls of the glassware and to facilitate cleaning.
To minimize loss, before disconnecting the transfer lines and condensers from the round-
bottom flask of the scrubber, pour approximately 100 ml of asbestos-free (filtered, distilled)
water down the exit condenser and another 100 ml down the transfer lines and entrance
condenser. Such rinsing should be performed in multiple stages, approximately 20 ml at a
time. Swirl each condenser (and the transfer lines) as the water drains into the flask. Tap-
each condenser (and the transfer lines) several times after rinsing to assure a reasonably
quantitative transfer. .
Detach and remove the round-bottom flask from the condensers and its stand and pour the
contents of the flask into a clean, pre-weighed, wide-mouthed 1 L plastic container. Rinse
the found bottom flask several times with additional asbestos-free water to assure a
quantitative transfer of any residual solids. Reweigh the container and record the net weight
as the total weight of suspension. If necessary, the sample may then be stored at ice
temperature until it can be prepared. However, preparation shall not be delayed for more
than 48 hours.
Immediately prior to filter preparation, add 1.5 g/L of sodium hexametaphosphate to the
suspension in the plastic container. Shake the suspension vigorously , and divide it
9-11,
-------
approximately evenly into two (or, if necessary, three) 500 ml Erlenrneyer flasks. Place the
flasks on a laboratory shake table for approximately three hours. Quickly re-combine the
contents of the two (or three) flasks into a clean, plastic container (with minimal flushing) and
place the container in a sonicator. Sonicate the suspension for approximately 1 minute (with
the power of the sonicator set at no more than 0.1 W/ml). Withdraw one ml with a disposable
pipette from the center of the volume of the suspension in the plastic container and dilute this
with asbestos-free water to 100 ml in a clean, volumetric flask.
The mass of respirable dust collected in the scrubber should be equal to the sum of the
cumulative mass of dust measured on the filters collected above the ME opening of the
elutriator over the entire run(s) during which the scrubber suspension was collected. Use this
estimated mass (and account for the 100-fold dilution performed as described in the last
paragraph) to estimate the size of aliquots required to produce filterable suspensions
containing: 0.5, 2, and 5 fig of respirable material. Dilute each aliquot to a minimum total
volume of 20 ml and filter each aliquot in the manner described in Sections 10.34 and 10.35
of the ISO Method for the determination of asbestos in air using an indirect transfer technique
(Chatfield 1993)28.
The filtered aliquots shall all be prepared as described in Section 10.1 and scanned briefly at
low magnification in the TEM to select the optimally loaded specimen for detailed analysis
(see Section 11.1.2).
9.5 CLEANING THE DUST GENERATOR
The dust generator is designed for quick and easy assembly and disassembly to facilitate
cleaning. Most of the joints are simple friction couplings or ring clamp couplings. To clean
the dust generator, disconnect and disassemble the tumbler, remove the bottom cup and
dust collector system from the elutriator, decouple the two halves of the elutriator tube,
disassemble the slide mechanisms of the dust collector and disconnect the transfer lines to
the scrubber. The metal pieces of the dust generator may then be washed with
biodegradable detergent, rinsed with asbestos-free water, sonicated briefly, and rinsed again.
The pieces may then be left to dry in room air or may be dried with a forced, HEPA-filtered air
stream.
The glassware of the scrubber shall also be washed with biodegradable detergent and
asbestos-free water, rinsed liberally, and dried in room air or dried with a forced, HEPA-filtered
air stream. It is recommend that new transfer lines between the elutriator and the scrubber-
(constructed of 1.00 in. i.d. Tygon tubing) be cut and installed after each cleaning.
23
As indicated in Chatfield (1993), filters to be employed for filtering scrubber suspensions are of a different type than
those employed in dust generator mounts. Filters used to filter scrubber suspension are to be the 0.22 urn pore size
variety -
9-12 . . .
-------
10.0 PREPARATION OF SPECIMEN GRIDS FOR TEM ANALYSIS
For Superfund applications of this method, asbestos analysis of all samples prepared using
the dust generator are to be performed on specimen grids prepared from aliquots of the
scrubber suspension. In addition, for a minimum of a subset of 5% (preferably 10%) or 10
samples (whichever is greater), asbestos analysis is also to be performed on specimen grids
prepared by a direct transfer technique from filters collected over the 1ST .opening of the
elutriator (i.e. the opening over the isokinetjc sampling tube). These analyses are then paired
with the analyses of asbestos from scrubber suspension collected during the same runs to
provide a link between samples prepared by each technique.
The primary reason for preparing 100% of samples from the scrubber suspension is to
facilitate identification of distinctions in sample characteristics; samples prepared in this
manner are expected to exhibit the best precision among the options for this method. At the
same time, when comparing results to published slope factors, the apparent need for
normalizing asbestos analyses to counts derived from directly prepared specimens (see, for
example, Berman and Crump 1989) is satisfied by providing a subset of samples prepared"
both ways to allow a regression to be performed linking results from the scrubber suspension
samples to specimens prepared by a direct technique. As indicated previously (Section
2.1.3), the recomrnended procedure is based on a compromise allowing optimum precision
for distinguishing among relative measurements (and relative risks) while excepting a small
reduction in the precision of estimates of absolute risk.29
10.1 PREPARATION OF SPECIMEN GRIDS FROM FILTERED ALIQUOTS OF THE
SCRUBBER SUSPENSION
Filters generated from aliquots of the scrubber suspension (as described in Section 9.4.6)
shall be prepared using the direct transfer technique that is described in Sections 10.5 of the
ISO Method (Chatfield 1993). As indicated previously, multiple aliquots representing a
sequence of dilutions are to be prepared to allow selection of the optimally loaded filters (and '
corresponding set of specimen grids) for final, detailed analysis.
From each filter, prepare a minimum of three specimen grids: one from near the center of the
filter, one from a location that is half the distance between the center and the outer edge, and
one from near the outer edge of the filter.
10.2 SPECIMEN GRID PREPARATION FROM FILTERS COLLECTED OVER THE 1ST
OPENING OF THE ELUTRIATOR
Although this method specifies that.filters collected over the 1ST opening of the elutriator shall
be prepared using a direct preparation technique, an indirect preparation technique is also
described, as an option for non-Superfund applications.
For other applications of this method, options might include preparation of 100% of samples from filters collected over
the 1ST opening of the elutriator and/or preparation of filters collected over this opening using an-indirect transfer
technique. The method is designed to be flexible.
10-1
-------
10.2.1 Specimen Grid Preparation Using a Direct Transfer Technique
Filters collected over, the 1ST opening of the elutriator (as described in Section 9.4.5) shall be
prepared using the direct transfer technique that is described in Sectiqn 10.5 of the ISO
Method (Chatfield 1993). As indicated previously, sections of multiple filters representing a
range of loadings are to be prepared to allow selection of the optimally loaded specimen
grids for final, detailed.analysis.
From each filter that has been collected over the 1ST opening, prepare four specimen grids
from locations on the filter that are each separated by 90° radially. Select two of the
locations (from opposing sides of the filter) at points that are about two thirds of the distance
from the center to the edge of the filter. The remaining two locations shall be selected at
points that are about one third of the distance from the center to the edge of the filter. Such
an arrangement will eliminate any effects potentially associated with a linear gradient across
the filter that may develop due to the brief time over which the filters are exposed to air flow
from the elutriator and, consequently, the potentially significant time during which the filter is
being slid in and out of alignment. .
10.3 Specimen Grid Preparation Using an Indirect Transfer Technique .
As an option to the procedure described in Section 10.2.1 above (for non-Superfund
applications only), filters collected over the 1ST opening of the elutriator (as described in
Section 9.4.5) may also be prepared using the indirect transfer technique that is described in
Sections 10.3 to 10.5 of the ISO Method (Chatfield 1993). For this option, multiple sections of
the most highly loaded .filter obtained from the dust generator shall be prepared using a
range of dilutions to allow selection of the optimally loaded specimen grids for final, detailed
analysis.
10-2
-------
11.0 PROCEDURES FOR ASBESTOS AND DUST ANALYSIS
11.1 PROCEDURES FOR ASBESTOS ANALYSIS .
Specimen grids prepared as described in Chapter 10 are to be analyzed using transmission
electron microscopy (TEM). Follow the procedures for analysis described in the ISO Method
(Chatfield 1993) including procedures for:
examining specimen grids to determine acceptability for analysis;
r structure counting by TEM (except determination of the stopping point);
structure morphological classification; . ~ .''."
structure mineralogical identification; and
blank and quality control determinations. ' - ~
The stopping points for the,analyses conducted in support of this method are a function of
the required sensitivity for the method and are defined in Sections 11.1.1 and 11 ^1.2 below.
Begin by examining one of each set of specimen grids derived for a defined loading from a
particular run of the dust generator and select the optimally loaded set for analysis. Use the
criteria for determining the acceptability of specimen grids (from the ISO Method) to define
optimal loading. ! ." '
When performing detailed analysis, be sure to distribute asbestos counts evenly over the
entire set of specimen grids prepared from a particular filter at a defined (optimal) loading.
Record the morphology and mineral type of asbestos structures as described in the ISO
Method (Chatfield 1993). Also as described in the ISO Method, .complete separate scans for
counts of total structures and, at lower magnification, for counts of structures longer than
5 -
11.1.1 Analysis of Specimen Grids Prepared from Filters Collected Over the 1ST
Opening of the Elutriator ,
Prior to initiating a detailed analysis of specimen .grids, the stopping rules for the analysis
must be defined. Assuming these specimen grids have been prepared using a direct transfer
technique (as discussed in Section 10.2), define the stopping rules for the detailed analysis
as follows.
. ; - ' , - , ! -
First, calculate the maximum number of grid openings that will have to be scanned during the
analysis from the relationship:
Ngo =
(11-1)
11-1
-------
where:
N
is the maximum number of grid openings to be" scanned;
Sd is the number of structures required to define detection using the
analysis (defined here as 1); ; . '
Af . is the total area of the filter from which the specimen grids were
prepared (mm2);
%RD is the mass percent of respirable dust in the sample and is defined
using Equation 11-9;
Ssmp, is the required analytical sensitivity for the method (s/g)';
Ago is the area of a single grid opening (mm2); and
AMfis the mass of respirable dust collected on the filter from which the
. specimen grids were prepared. It is defined using Equation A-7 of
Section A.2.2 of Appendix A (g).
The following are typical values for the above parameters:
smpi
°/
AM
f
5x10' (for total structures) or
3 x TO6 [for structures longer than 5 fim)30;
382 mrrn , ,
= 8.1
between 0.5% and 2%31; and
32.
Given the above values, it is estimated using Equation 11-1 that between 1 and 4 grid
openings will.typically need to be scanned to derive a count of total structures. However, a
minimum of 4 grid openings shall be scanned during any analysis. Based on the above,
similarly, between 15 and 62 grid openings will typically need to be scanned to derive a count
of structures longer than 5 jim.
The number of grid openings to be scanned for specific analyses shall be determined by
substituting case-specific values for the above listed parameters into Equation 11-1.
Stop the counting, characterization, identification, and recording of asbestos structures on a
particular analysis when one of the following obtains:
30 See Section 2.1.1.
31 This is the range of values observed for a diverse variety of samples tested during the pilot study for this method
(Berman et al. 1994a). ,
See Sections 9.4.5 and A.2.2 of Appendjx A.
11-2
-------
the scan is completed for the grid opening on which the 50th asbestos structure
is counted; or '...'..-
i -,.-
either 4 grid openings or the maximum number of grid openings (estimated as
defined.above), whichever is greater, are scanned completely. ,
1 . *
These rules are to be applied separately to the scan for total structures and the scan for long
structures (i.e. longer than 5 jim) that are described in the ISO Method.
. 11.1.2 Analysis of Specimen Grids Prepared from Filtered Scrubber Suspension
Prior to initiating a detailed analysis of specimen grids, the stopping rufes for the analysis
must also be defined in this case. Given that these specimen grids have been prepared as
described in Section 10.1, define the stopping rules for the detailed analysis as follows.
, First, calculate the maximum number of grid openings that will have to be scanned during the
analysis from the relationship:
Ngo = Sd*Af*%RD*DF/(Ssmp|*Ago*100*Mscrbr)
(11-2)
where:
NL,
is the maximum number of grid openings to be scanned;
Sd is the number of structures required to define detection using the
analysis (defined here as 1);
Af is the total area of the filter from which the specimen grids were
prepared (mm2);
%RD is the mass percent of respirable dust in the sample and is defined
using Equation 11-9;
Ssmp| is the required analytical sensitivity for the method (s/g);
,2s.
90
DF
is the area of a single grid opening (mm );
is the dilution factor by which the scrubber suspension -had to be
diluted to prepare' specimen grids that are suitably loaded for
analysis; and
Mgcrbr is the mass of respirable dust collected in the scrubber suspension
during the run.
The dilution factor, DF, is simply the product of the individual dilution factors for the two
sequential dilutions performed to derive the final volume that is ultimately filtered (per the
procedure defined in .Section 9.4.6):
11-3
-------
DF =
(11-3).
where:
Vs is the volume of the initial scrubber suspension (which is estimated from
the recorded weight of the supernatant assuming a density of 1 g/cm3)
(ml); ' ,
Va1 is the volume of the first aliquot collected from the scrubber suspension
for further preparation (the default defined in Section 9.4.6 is 1 ml);
Vd is the volume into which the first aliquot from the suspension is diluted
(the default defined in Section 9.4.6 is 100 ml); and
V^ is the volume of the final aliquot collected from Vd that is ultimately
filtered for preparation of the optimally loaded specimen grids (ml).
The mass of respirable dust collected in the scrubber suspension, Mscrbr, is derived from the
cumulative mass of dust collected during the run on filters that are mounted over the ME
opening of the elutriator (defined below as Mf). These differ by the ratio of the air flow into
the filters and the air flow into the scrubber:
Mscrbr = Mf*
(11-4)
where:
Mscrbr is tne mass of respirable dust collected in the scrubber during the
run(g); .
Mf is the cumulative mass of dust collected on the filters (mounted over the
ME opening of the elutriator) during the same run (calculated from
Equation A-4 of Section A.2.1 . of Appendix A);
Fs is the volumetric air flow rate into the scrubber (cm3/s); and
Fc is the volumetric air flow rate into the filters over the ME opening of the
elutriator (cm3/s).
Assuming air flow in the elutriator is setup as described in Section 9.3.4, Fs and Ff are equal
so that Mscrbr simply equals Mf.
Given the typical values for the corresponding parameters provided in Section 11.1.1,
assuming a typical value for DF ^ of between 2 x 10* and 4 x 104, and selecting a range of
typical values for Mf (i.e. between 0.1 and 0.2 g) from among the range observed during the
pilot study (Berman et al. 1994a), it is estimated using Equation 11-2 that between 1 and 8
grid openings will need to be scanned to derive counts of total structures. Similarly, it is
estimated that between 8 and 133 grid openings will need to be scanned to derive counts of
long structures (i.e. longer than 5
This assumes typical values for M, (between 0.1 and 0.2 g) from among the range of values observed among diverse
samples during the pilot study. (Berman and Kolk 1994) and further assumes that the dilution factor is selected so as to
produce a loading of 5 fig on the fitter. '.
'^
11-4 -
-------
Determine the actual number of grid openings required for a specific analysis by substituting
case-specific values for the above parameters into Equations 11 -2, 11 -3, and 11 -4,
Stop .the counting, characterization, identification, and recording of asbestos structures on a
particular analysis when one of the following obtains:
> the scan is completed for the grid opening on which the 50th asbestos structure
is counted; or
either 4 grid openings or the maximum number of grid openings (estimated as
defined above), whichever is greater, are scanned completely.
These rules,are to be applied separately to the scan for total structures and the scan for long
structures (i.e. longer than 5 jim) that are described in the ISO Method (Chatfield 1993).
' ' » - ,
11.2 EVALUATING THE RATE OF RELEASE OF RESPIRABLE DUST
The rate of release of respirable dust from a sample prepared using the dust generator is
estimated from measurements of the mass of dust collected over time on the set of filters
mounted over the ME opening of the elutriator. The measurements used specifically are from
those filters that are collected while the tumbler is operating at the highest rotation rate
employed for the sample (see Section A.2.1 of Appendix A). '
Begin by plotting the cumulative mass collected on the filters as a function of time. To derive
the cumulative mass for a particular time interval, add the mass of dust measured on the filter
collected from that time interval to the sum of the masses measured on the set of filters"
collected earlier in the run. Typical curves are depicted in Figures 11-1 and 11-2. Next,
calculate the cumulative mass released from the sample over time from the cumulative mass
collected on filters over time using the relationship developed in Section A.2.1 of Appendix A:
r = 2.1*Mf
(11-5)
where:
Mr is the cumulative mass of dust released from a sample between the start of a
run and time T (g); and '
Mf is the cumulative mass collected on filters34 between the start of a run ,and
time "t" (g).
Equation 11-5 is appropriate to use to relate the mass of dust collected on filters to the mass
released from the sample when air flow in the dust generator is setup as indicated in Section
9.3.4. If different air .flow conditions are established for a particular experiment, the
relationship between Mr and Mf will have to be derived using Equation A-4 from Appendix A.
These are the fitters that are mounted over the ME opening of the elutriator.
11-5
-------
FIGURE 11-1
TYPICAL CUMULATIVE MASS RELEASE
VERSUS TIME CURVE FOR 30 RPM RUN3
CO
DC
2.
a
t
CO
o
a.
UJ
a
CO
CO
a
U
100
200
300
400
TIME (MINUTES)
KEY:
DUST SAMPLE MEASUREMENT
BEST FIT LINE
3FROM THE 30-RPM RUN ON SAMPLE 1-100, WHICH WAS COMPLETED
ON 8/27/93 DURING THE PILOT STUDY (BERMAN ET. AL. 1994a).
-------
FIGURE 11-2
TYPICAL CUMULATIVE MASS RELEASE
VERSUS TIME CURVE FOR 60 RPM RUN8
^ 0.14
CO
a
ia
to
o
a
ui
a
CO
CO
Q
UI
1
ID
O
0.00
200
400
TIME (MINUTES)
KEY:
DUST SAMPLE MEASUREMENT
BEST FIT LINE
8FROM THE 60-RPM RUN ON SAMPLE 1-100, WHICH WAS COMPLETED
ON 8/27/93 DURING THE PILOT STUDY (BERMAN ET. AL. 1994a).
-------
The total mass of dust in the sample at the beginning of the run must next be estimated using
the relationship developed in Appendix A. Based on the relationship (see Section A.2.1):
ln(M0 - Mr) = ln(M0) - kt - (11-6)
where:
M0 is the mass of dust in the sample at the start of the run (g);
k is the first-order rate constant for the release of dust from the sample (s~1);
and. ,
t is the time since the start of the run (s);
/
a plot of ln(M0 - Mr) versus t should be a straight line with a slope equal to the rate constant
for the release of dust from the sample and an intercept equal to the natural logarithm, of the
mass of dust in the sample at the start of the run. Derive estimates of "M0" and "k" by
programming Equation 11-6 into a spreadsheet and running a regression35.
Input a range of guesses for the value of M0 into the spreadsheet and run a regression to fit
a value for k and to calculate a Value for the regression coefficient, "r^" for each value of M0.
Plot the regression coefficient, "r2" as a function of M0. An example of such a plot is
presented in Figure 11 -3. The value of M0 that provides the fit with the largest regression
coefficient (i.e. with ^closest to 1) shall be reported as the correct value for the mass of dust
in the sample at the start of the run and shall be reported with the corresponding k value as
the estimated rate constant for dust release from the sample during the run.
11.3 DETERMINING THE CONTENT OF RESPIRABLE DUST
To determine the mass percent of respirable dust in the original sample, first determine the
total mass of respirable dust in the sample at the start of a run for the last run completed on
the sample, which is derived as described in the last section.
Because the dust generator run analyzed as described in Section 11.2 will generally have
been preceded by a run with the tumbler speed set at 30 rpm (see Section 9.4.4), to estimate
the total mass of dust present in the sample, it is necessary to include the mass released
during this first run.
Sum the masses of dust measured on each of the filters collected during the 30 rpm run and
designate this sum, "M^", which is the cumulative mass of dust collected .during the 30 rpm
run. Using the following equation, estimate the total mass of dust released from the sample
during the 30 rpm run, "M^," based on the mass of, dust collected during that run (see
Section A.2.1 of Appendix A):
= 2.08'M^
(11-7)
35 Any of several commercial spreadsheet programs (including, for example, LOTUS) contain the necessary capabilities
and may be employed to derive optimum values for 'M ' and "k." '
11-8
-------
FIGURE 11-3
ILLUSTRATION OF THE OPTIMIZATION
OF THE ESTIMATE OF INITIAL MASS "Mn
A. TYPICAL PLOT OF CORRELATION COEFFICIENT VERSUS INTITIAL MASS FOR A DUST GENERATOR RUN3
.' - . 1-
CM
DC
UJ
O
u.
U.
1U
O
O
HI
DC
DC
8
0.9995
0.9965
0.16 0.18 0.2 0.22 0.24 0.26 0.28 0.3
TIME (MINUTES)
B. TYPICAL PLOT OF THE OPTIMIZED FIRST ORDER RATE EQUATION FOR A DUST GENERATOR RUN3
-1.5
CM
CM
O
y = 1.51-0.00379 *x
R2 = 1.000
100
TIME (MINUTES)
100
aFROM THE 60-RPM RUN ON SAMPLE 1-100, WHICH WAS COMPLETED
ON 8/27/93 DURING THE PILOT STUDY (BERMAN ET. AL. 1994a).
-------
Calculate the total mass of dust originally present in the sample, Mtot, by summing the mass
released during the 30 rpm run with the mass of dust estimated to have resided in the sample
at the beginning of the higher rpm run, M0 (this is equal to the mass of dust remaining in the
sample at the end of the 30 rpm run). M0 will have been derived as described in Section
11.2: , ,
Mtoi = Mrso + Mc
(11-8).
Estimate the mass percent of respirable dust in a sample as follows:
%RD = 100*Mtot/Msamp|e (11-9)
where: . ' "
%RD is the mass percent of respirable dust in the sample (%); and
^sample 's *ne mass °ftne original sample placed in the tumbler (g).
11.4 DETERMINING THE CONTENT OF ASBESTOS
The concentration of asbestos in a sample is determined differently depending on whether
asbestos is determined from sampling grids prepared from filters collected over the 1ST
opening of the elutriator or from scrubber suspension.
NOTE
For samples originally containing a significant fraction of coarse material (see Section
.8.4), the concentration of asbestos reported as a function of the mass of the sample
(specified in'this section) must be adjusted for the quantity of coarse material originally
measured in the matrix sampled in the field before it can be considered representative
of that matrix. A procedure for adjusting asbestos concentrations to account for the
coarse fraction of an environmental matrix is presented in Section 11.4.3.
11.4.1 Based on Directly Prepared Filters Collected Over the 1ST Opening of the
Elutriator
Procedures for determining the concentrations of asbestos structures in a sample differ
sligTitly depending on whether the structures of interest are longer or shorter than 5 urn.
Structures that are shorter than 5 jim in length are derived only from the high magnification
scan of an analysis. Calculate and report the concentration of short asbestos in the original
sample based on the counts of asbestos structures that are derived as defined in Section
11.1.1 using the following relationship:
11-10
-------
Csmpl = Sch*V%RD/(Ngoh*Ago*100*AMf)
(11-10)
where:
Csmp| is the concentration of asbestos structures (of a defined size range
or type) in the original sample (s/g); , , .
Sch is the number of structures (of the defined size range or type of
interest) counted during the high magnification scan of the analysis;
is the total area of .the filter from which the specimen grids were
prepared (rnm2);
V
%RD
is the mass percent of respirable' dust in the sample and is defined
using Equation 11-9 (%); x '
Ngoh is the number of grid openings scanned during the high
magnification scan of the analysis;
is the area of a single grid opening (mm2); and
if is the mass of respirable dust collected on the filter from which the
specimen grids were prepared. It is defined using Equation A-7 (see
Section A.2.2 of Appendix A) (g).
"go
AM
Structures that are longer than 5 jim in length are derived from combined counts collected
during both the high and low magnification scans of an analysis. Calculate and report the
concentration of long asbestos in the original sample based on the counts of asbestos
structures that are derived as defined in Section 11.1.1 using the following relationship:
where:
C
'smpl = (Sch + Sc,)*V%RD/|;(Ngoh + Ngol)*Ago*100*AMf] (11-11)
.smp! is the concentration of asbestos structures (of a defined size range
or type) in the original sample (s/g);
3ci is the number of structures (of the defined size range or type of
interest) counted during the low magnification scan of the analysis;
and .
Ig0i is the number of grid openings scanned during the low
magnification scan of the analysis.
N
Thus, for long structures, it is the total counts of structures observed over both the high and
low magnification scans and the total area scanned (over both the low and high magnification
scans) that are used to determine concentration.
11-11
-------
As an option, asbestos concentrations may also be reported as a function of the mass of
respirable dust in a sample using the following relationships. For short structures, use:
Cdust = Sch*Af/(Ngoh*Ago*AMf) -
(11-12)
where:
C
dust is the concentration of asbestos structures (of any defined size
range or type) in the respirable dust of the sample (s/gdust); and all
other parameters are defined as described above.
Similarly, for long structures, use:
st = (Sch + Sc|)*Vt(Ngoh + Ngo|)*Ago*AMf]
1 1 .4.2 Based on Specimens Prepared from Scrubber Water
(11-13)
As described in Section 11.4.1, procedures for determining the concentrations of asbestos
structures in a sample differ slightly depending on whether the structures of interest are
longer or shorter than 5
Structures that are shorter than 5 jim in length are derived only from the high magnification
scan of an analysis. Calculate and report the concentration of short asbestos in the original
sample based on the counts of short asbestos structures that are derived from the scrubber
suspension as defined in Section 11.1.2 using the following relationship:
Csmp! = Sch*V%RD*DF/(Ngoh*Ago*100*Mscrbr)
(11-14)
where:
Csmp, is the concentration of asbestos structures (of a defined size range
or type) in the original sample (s/g);
Sch is the number of structures (of the defined size range or type of
interest) counted during the high magnification scan of the analysis,;-
Af is the total area of the filter from which the specimen grids were
prepared (mm2);
%RD is the mass. percent of respirable dust in the sample and is defined
using Equation 11-9 (%);
N
goh
is the number of grid openings scanned during the high
magnification scan of the. analysis;
is the area of a single grid opening (mm2);
11-12
-------
DF is the dilution factor by which the scrubber suspension had to be
diluted to prepare specimen grids for analysis (derived as defined in
Equation 11-3); and -
Mscrbr is the mass of respirable dust cpllected in the scrubber suspension,
during the run (derived as defined in Equation 11-4).
Structures that are longer than 5 jim in length are derived from combined counts collected
during both the high and low magnification scans of an analysis. Calculate and report the
concentration of long asbestos in the original sample based on the counts of long asbestos
structures that are derived from scrubber suspension as defined in Section 11.1.2 using the
following relationship:
smpl
where:
C
Ngo,)*Ago*1 00*Mscrbr]
(11-15)
s | is the concentration of asbestos structures (of a defined size range
or type) in the original sample (s/g);
c| is the number of structures (of the defined size range or type of
interest) counted during the low magnification scan of the analysis;
and
N
'goi
is the number of grid openings scanned during the low
magnification scan of the analysis.
f
As an option for analysis of the scrubber suspension, asbestos concentrations may also be
reported as a function of the mass of respirable dust in a sample using the following
relationships. For short structures, use: . , :
Cdust = Sch*Af*DF/(Ngoh*Ago*Mscrbr)
(11-16)
where: -. . -
Cdust is the concentration of asbestos structures (of any defined .size
range or type) in the respirable dust of the sample (s/g^gt); and all
other parameters are defined as described above.
Similarly, for long structures, use:
Cdust =
Sc))*Af*DF/[(Ngoh + Ngo,)*Ago*Mscrbr]
(11-17)
11-13
-------
11.4.3 Procedure for Adjusting Asbestos Concentrations to Account for the
Presence of Coarse Material in the Sampled Matrix
As indicated in Section 8.4, due to the need to incorporate field data into this calculation, a
formal protocol designating who is to perform this calculation and how that individual is to
obtain the needed field information must be defined at the start of a study using this method.
To provide a representative measure of the concentration of asbestos jn an environmental
matrix in which significant coarse material is found (i.e. more than 10% by weight), first derive
an appropriate coarseness adjustment factor:
CF = Mfrne/(Mfi
ne Mcoarse)
(11-18)
where:
CF
is the coarseness adjustment factor for a particular sample
(dimensionless);
Mfjne is the mass of fine material measured immediately after sieving the
sample in the field (g); and
Mcoarse is tne mass °f coarse material measured immediately after sieving
the .sample in the field (g).
Then, to determine the concentration of asbestos in the environmental matrix that was
sampled, perform the following adjustment:
Cmtrx = CF*Csmpl
(11-19)
where: .
CF is the coarseness adjustment factor for a particular sample (derived
as defined above);
Cmtrx is the concentration of asbestos structures (of a defined size range
or type) in the field matrix sampled '(s/g); and :
Csmp, is the concentration of asbestos structures (of a defined size range
or type) in the sample sent to the laboratory (s/g). This is
determined as described in Sections 11.4.1 and 11.4.2 above.
11-14
-------
12.0 PERFORMANCE CHARACTERISTICS AND QUALITY CONTROL/QUALITY
ASSURANCE REQUIREMENTS
12.1 METHOD PERFORMANCE
The method defined in this document achieves the target performance requirements defined
in Section 2.1 at a cost that should be competitive with other procedures that might be
designed to produce comparable information (Section 2.4).
12.1.1 Analytical Sensitivity
As indicated in Section 11.1, depending on sample characteristics, between 1 and'8 grid
openings will likely have to be scanned at high magnification (20,000x) to achieve the target
analytical sensitivity for total asbestos structures of 5x107 s/gso|id. Similarly, between 15 and
133 grid openings will likely have to be scanned at low magnification (10,000x) to achieve the
target analytical sensitivity for long asbestos structures (longer than 5 |im) of 3x106
The defined sensitivities for total and long structures were, easily
study for the method (Berman et al 1994a).
12.1.2 .Precision
the pilot
Results of the pilot study for this method (Berman etval,1994a) indicate that, when 50
structures are counted, the average relative percent difference observed among eight sets of
duplicate samples (four sets of duplicate samples analyzed by each of two laboratories) is
20%. ,
The precision of an asbestos measurement (in this case, expressed as the relative percent
difference) should be inversely proportional to the square root of the number of structures
counted. Given that 1 0 structures are likely to be counted at the target concentrations for this
method (see Section 2.1.1) and, based on the precision observed in the pilot study when 50
structures are counted, it is expected that the average relative percent difference achievable
for this method should be 43% at the target concentrations listed in Section 2.1.1. Thus,
given the analytical sensitivities defined in Section 2.1.1 and the stopping rules defined in
Section 11.1, this method is capable of achieving a level of precision that is comparable with
the guidelines recommended in the CLP for the analysis of other, analytes in soils and defined-
f or this method in Section 2.1.2. - -
The precision observed during the pilot study for this method is based on specimen grids
prepared from the suspension collected in the scrubber of the elutriator (Appendix A). It is
expected that the precision achieved for analyses derived from scans of specimen grids
derived by direct preparation of filters collected over the isokinetic sampling tube of the dust
generator (see Appendix A) will be significantly worse. Procedures are therefore incorporated
into this method in which the majority of samples will be analyzed based on preparation of
specimen grids from filtered scrubber suspension with a subset of 5 to 10% simultaneously
analyzed using specimen grids prepared by a direct transfer technique from filters collected
over the isokinetic sampling tube of the elutriator (see Chapter 10). The latter is required to
develop a regression relating these two types of preparations so that measurements can be
evaluated using existing dose-response factors for asbestos (see Section 2.1.3); existing
12-1
-------
dose-response factors tend to be based on the analysis of samples whose preparation
corresponds most closely to a direct preparation.
NOTE
It is anticipated that a direct, linear relationship will be observed between asbestos
concentrations derived, respectively, from scrubber suspension and from filters
collected over the 1ST opening of the elutriator for samples collected from the same
environmental matrix. However, there is little reason to expect that such a relationship
will hold across samples collected from different environmental matrices. Therefore,
samples to be employed to determine the relationship between asbestos measured
from scrubber suspension and from filters mounted over the 1ST opening of the
elutriator should be selected and evaluated separately for each environmental matrix
sampled during a study for analysis using this method.
It must be recognized that compromises are required when developing a method of this type.
The proposed reporting of samples prepared primarily by an indirect technique with a small
subset of directly prepared samples (the latter used primarily to provide a link between the
reported measurements and existing dose-response factors) represents such a compromise.
The proposed procedure allows for the determination of relative concentrations with maximum
precision so that arbitrarily small differences in concentrations can be easily distinguished.
Among other things, this will facilitate distinguishing upwind and downwind concentrations by
a source. At the same time, somewhat lower precision is considered acceptable for
estimating the absolute risk associated with any particular measurement.
NOTE
The uncertainty of the proposed regression to link results from directly and indirectly
prepared samples is expected to be attributable almost exclusively to.the limited
precision of the directly prepared samples. Therefore, use of the proposed regression
for estimating risks may not significantly increase the uncertainty of such a risk
analysis beyond what would be associated with assigning an estimated risk to an
asbestos concentration derived from a directly prepared sample in any case.
It is also assumed that a sufficient number of samples (i.e. a minimum of approximately
10) will be co-prepared and analyzed to allow reasonable confidence in the results of
the regression. '
12.1.3 Accuracy
Based on the results of the pilot study (Berman et al. 1994a), there appears to be a problem
with laboratory bias during the counting of asbestos structures in support of this method.
The bias is introduced specifically during the analysis of specimen grids because duplicate
samples prepared by the same laboratory using identical procedures nonetheless yield
significantly different counts by analysts from each of two laboratories.
12-2
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Given that analysts within a single laboratory appear to be capable of achieving good
agreement on counting (also demonstrated in the pilot study), the problem of between-
laboratory bias will need to be addressed by the implementation of an aggressive inter-
laboratory quality control (QC) program in which samples are regularly shared among
laboratories and a procedure for verified counting is instituted... It may also be useful to
promote meetings with discussion sessions in which analysts from different laboratories
discuss the interpretation of structures viewed simultaneously (either directly from a
microscope or from a video). \ , ,
12.1.4 Asbestos Characteristics,
v . ' ' '
As was observed during the pilot study (Berman et al. 1994a), this method is easily capable
of preserving information concerning the distribution of the sizes and shapes of asbestos
structures that are likely to be released from environmental matrices that are disturbed by
natural or anthropogenic forces. As indicated in Section 2.1.3, such'information is critical to
evaluating the potential health effects of the asbestos dusts generated by releases from
asbestos-containing matrices (see, for example, Berman and Crump 1989).
Interferences and limitations concerning the ability to identify and characterize asbestos
structures using the counting and identification rules of the ISO Method, as adopted for this
method (Section 11.1), are described in the ISO Method (Chatfield 1993).
' - ( , ' ' -* .
12.1.5 Reporting Requirements
As indicated in Section 11.4, the concentrations of asbestos structures (of any defined size or
type) that are measured using this method can be easily reported either as a function of the
mass of the sampled material or as a function of the mass of respirable dust in the sampled
material. This should allow sufficient flexibility to facilitate use of results from this method in
concert with any of the fate, and transport models that may be employed to predict exposure
(Section 2.1.4). .
12.2 QUALITY CONTROL REQUIREMENTS
The quality assurance/quality control (QA/QC) requirements indicated in the ISO Method
(Chatfield 1993) shall be considered relevant and appropriate when using this method. In
addition, the following blank -and duplicate/replicate schedule shall be employed when
running samples using this method. " .-..-_
12.2.1 Blanks
' . ' *> ' ' . .
The following blanks shall be collected routinely in concert with use of this method: ,
lot blanks or filter blanks. Two filters from each lot of 50 filters obtained from the
manufacturer shall be prepared using a direct transfer procedure and analyzed to
assu're that background contamination on the filters does not- exceed 10s/mm2
(Section 6.6). Only filters from lots whose blanks pass the defined criterion shall
be used in support of this method;
laboratory blanks. A sufficient number of laboratory blanks shall be collected,
prepared using a direct transfer technique and analyzed to show that the room in
12-3
-------
which bulk samples are handled and prepared satisfy the requirements defined in
Section 10.6 of Chatfield and Berman '(1990). When laboratory blanks indicate
that room air is out of compliance with the stated criterion, use of this method is
to cease until appropriate corrective actions are completed;
field blanks. Field blanks shall be collected during any sample collection
activities performed in association with use of this method. The number of such
blanks to be collected and the schedule for their analysis shall be determined
based on the complexity of the anticipated sampling scheme and shall be
defined as part of the sampling plan for the site. QC criteria for field blanks will
also be set as part of the planning for the study;
equipment blanks. Equipment blanks are collected at the beginning of each run
of the dust generator, as described in Section 9.4.3. Equipment blanks do not
generally need to be analyzed on a regular basis but shall be stored in case their
use is required to help determine the source of contamination that may be
discovered by some other means;
run blanks. Run blanks are also collected at the beginning of each run of the
dust generator, as described in Section 9.4.3. One run blank shall be analyzed
routinely for the first run completed on any particular sample. The remaining run
blanks generated in association with a particular sample shall be stored in case
their use is required to help determine the source of contamination that may be
discovered by some other means.
Should asbestos structure counts on run blanks exceed the target criterion of
10s/mm2, use of this'method shall cease until appropriate corrective actions
have been completed and new run blanks are shown to achieve the stated
criterion; and
scrubber blanks. Scrubber blanks shall be derived by collecting a 1 ml aliquot of
scrubber liquid (after the scrubber is loaded and assembled for a run but before
heating of the scrubber is initiated), diluting the aliquot to 10 ml, and completing
the preparation of the diluted aliquot as described in Section 9.4.6. Scrubber
blanks do not need to be analyzed routinely but shall be stored in
case their use is required to help determine the source of contamination that may,
be discovered by some other means.
In addition to the above listed blanks that must be collected routinely in association with use
of this method, the following may prove helpful for identifying the source of any contamination
that might be detected in association with use of the dust generator:
modified run and scrubber blanks. Modified run and scrubber blanks may be
generated by setting up and operating a clean dust generator without sample.
Filters may be collected from either the ME or the 1ST opening of the dust
generator at. any point of such a run. Similarly, aliquots of scrubber liquid may
be withdrawn from the scrubber at any point. Such blanks may prove useful for
determining whether contamination is being introduced by any of the
components of an operating dust generator (including, for example, the constant
12-4
-------
humidity solution, the rotating tumbler, the elutriator tube, the air transfer lines,
and/or the glassware or liquid of the boiling scrubber); and
post-run scrubber blanks. , A post-run scrubber blank may be generated by
repeating the rinse of the transfer lines, condensers, and scrubber flask
immediately after the quantitative rinse conducted for a particular sample (see
Section 9.4.6). The resulting liquid must then be weighed, diluted quantitatively,
and prepared in the same manner as described for the scrubber suspension of a
sample (Section 9.4.6). The normalized concentration of asbestos structures
found in such a blank shall represent no more than 10% of the concentration of
asbestos structures observed in the sample prepared immediately prior to
collecting the post-run blank. Higher blank concentrations shall be considered
unacceptable. If blank concentrations are observed, procedures for quantitative
rinsing shall be reviewed, modified, and tested until losses can be shown to be
acceptable.
NOTE -
'- -* '
Asbestos observed in post-run blanks constitute asbestos that is lost from a
sample during preparation. ' .
12.2.2 Duplicates/Replicates
A fixed fraction (5 to 20%) of the samples collected in the field in support of this method shall
be collected as spatial duplicates ('two samples collected at immediately adjacent locations).
These shall be labeled and sent to the laboratory in such a manner so as to assure that
laboratory personnel cannot identify them as duplicates. The frequency of collection of
spatial duplicates shall be defined as part of the sampling plan for the site. Comparison of
the results of the analysis of such samples provides a measure of all of the components of
total precision except population variability.
As indicated previously (Section 8.2.1), 100% of the samples shipped from the field are to be
shipped as duplicate pairs. The laboratory shall randomly select 10% of the duplicate
samples shipped from the field and shall analyze both samples of the pairs so selected.
Comparison of the results of the analysis of such samples, which are homogenized splits of
the same sample, provides an Indication of the precision achieved by sample preparation and
analysis. ,
Should analysis of duplicate pairs indicate an unacceptable degree of variability (i.e. a relative
percent difference greater than 50%), replicate counts shall be performed on designated
samples by multiple analysts in the laboratory (or by the same analyst on different days).
Laboratory management shall assign such counts so as to assure that analysts cannot
determine which counts are replicates. Results of such replicate counts shall serve to
distinguish,whether the major source of variability observed among duplicate pairs is due to
analysis or to sample preparation. Appropriate corrective actions may then be devised.
12-5
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13.0 REPORTING REQUIREMENTS
13.1 FIELD AND LABORATORY NOTEBOOKS
Over the course of the project, information critical to the proper reporting and interpretation of
each sample analysis will be developed both in the field and in the laboratory. .Formal
procedures are required to preserve such information and to allow for the documentation of
attendant information that, while not employed directly in the calculation of results, may
provide insight into the interpretation of such results.
13.1.1 Field Notebooks
During sample collection, detailed notes will be kept in a stan'dard field or laboratory
notebook that is bound and pre-paginatedi All entries to the notebook are to be dated and
initialed. Information to be recorded during sample collection should include (but is not
limited to): . ,
(a) reference to this method; '
(b) the project title, identification of the site, and the names and titles of field
personnel participating in the sampling effort; ,
(c) identification of each sample or fraction of each sample handled in the field;
'(d) the date and time that each sample was collected and the time interval during
which each sample was prepared in the field;
(e) the location from which each sample was collected and the manner in which
sample locations were selected (including reference to the sampling plan under
which sampling was conducted); .
(f) - a general description of the physical appearance of the materials sampled;
(g) the types of equipment and the procedures employed to collect each sample;
(h) a summary of the procedure employed for field preparation of each sample"
(including, for example, the number of passes through a riffle splitter employed
for homogenization, and the number of splits required to reduce the sample to
the size required);
(i) the relevant identities and weights of each fraction of sample handled during field
preparation (including specifically the weights of the coarse and fine fractions
separated from each sample during sieving); , ^
(j) other relevant field observations (including, for example, the meteorological. ,
conditions under which sampling was conducted); and
(k) the identification, weight, and intended destination of each sample shipped from
the field.
13-1
-------
13.1.2 Laboratory Notebooks .-.'.-
During sample handling, preparation, and analysis, detailed notes will be kept in a laboratory
notebook that is bound and pre-paginated. All entries to the notebook are to be dated and
initialed. Information to be recorded during sample preparation and analysis should include
(but is not limited to):
(a) reference to this method; . ' ' .
(b) identification of each sample 'or fraction of each sample received from the field
and the date and time that each sample was received;
(c) identification of all laboratory personnel who participate in the preparation and
analysis of samples and the specific operations performed by each;
(d) identification of reagents, equipment, and supplies employed during sample
handling, preparation, and analysis;
(e) relevant material weights and/or volumes;
(f) the lot number and manufacturer of the filters employed during sample
preparation;
(g) a summary of the procedure employed for laboratory preparation of each sample
(including, for example, the number of passes through a riffle splitter employed
for homogenization and the number of splits required to reduce the sample to the
size required);
(h) the relevant identities and weights of each fraction of sample handled during
laboratory preparation;
(i) the setup conditions employed for the dust generator (including, for example, the
identity of the salt employed for humidity control, air flow conditions, and the
setting on the variable voltage transformer employed for the scrubber);
(j) the date and starting time, description (including, primarily, the tumbler rotational
speed), and sample identification for any run conducted on the dust generator;
(k) the weight and identity of the sub-sample placed in the dust generator;
(I) the identities, time intervals of collection, the starting and ending weights, and the
net weights of filters collected during a run on the dust generator that are to be
used to determine the rate of dust generation;
(m) the figures and calculations employed to determine the rate of dust generation
and the quantity of dust in the sample;
(n) the identity, time interval of collection, starting and ending weights, and the net
weights of filters collected during a run on the dust generator that are to be used
to generate specimen grids for asbestos analysis;
13-2
-------
(o) the identity, time interval of collection, the weight/volume, dilution factor, aliquot
identification, and filter identification for the collection, handling, and filtering of
scrubber suspension;
(p) the identity of all filter sections used for preparation of specimen grids and the
identity of the specimen grids (include a description of the sector and radial
distance from the center of the filter represented by each section);
. (q) energy levels and settings for.instruments employed for analysis;
(r) flow rates, pressures, temperatures, and other relevant physical parameters that
potentially impact prpcedures;
(s) room conditions (i.e. temperature, relative .humidity, and ventilation rates)
prevailing during sample preparation;
(t) other relevant observations (including, for example, any difficulties encountered
during preparation and analysis and any procedural changes incorporated into"
the method that are necessitated by such difficulties);
(u) documentation of all calculations performed in support of preparation and
analysis;
(v) all relevant QA/QC measurements (including the results of the analysis of all
blanks, duplicates, and replicates-see Chapter 12); and
: (w) a detailed time log of events including the time that particular procedures are
initiated and completed for each sample.
13.2 FIELD ACTIVITIES REPORT
To assure that the field information required to complete estimation of dust and asbestos
concentrations and release rates are provided to the data users, a field activities report must
be completed and must be submitted to the laboratory along with the corresponding
samplesi Laboratory personnel are then to attach this report directly to their batch report,
which shall cover the corresponding batch of samples.
The field activities report shall include the following for each sample batch, at a minimum:
(a) the project title and the identification of the site;
(b) reference to this method; ,
(c) reference to the sampling and analysis plan under which samples were collected;
' *' i
(d) a brief description of the objectives for sampling;
(e) a brief description of the procedures employed for selecting sampling locations
and the motivation for employing such procedures;
13-3
-------
(f) for'each sample in the batch accompanying the report:
the identifier for each sample fraction submitted to the laboratory;
the identifier for the original sample from which each submitted sample
fraction was derived; _
the type of equipment and reference to (or a brief description of) the
procedures employed for collection of the original sample;
the coordinates at which each original sample was collected36;
the total mass of the original sample from which each sample fraction
originated and the masses of the coarse and fine fractions separated during
^sieving of the sample in the field;
a brief description of the procedures employed for sample homogenization
and for sample splitting;
- the date and time that each sample was collected and the date and time that
each sample fraction was prepared in the field; and
a brief discussion of any deviation from the sampling and analysis plan not
covered in e.
An example of the format to be employed for a field activities report is provided in Figure
13-1. .
13.3 SAMPLE ANALYSIS REPORT
The sample analysis report for each sample shall include the following at a minimum:
(a) reference to this method;
(b) reference to the sample identification and batch number for the sample;
(c) the date and site from which the sample was collected;
(d) the weights and identities of the coarse and fine fractions of the sample and the
sub-sample of the fine fraction sent for analysis;
(e) the weights and identities of any splits or other fractions of the sample generated
during laboratory preparation;
(f) the weight and identity of the sub-sample placed in the dust generator;
H the submitted sample fraction is a sub-sample of a composite, what should be described here is the specific area of
concern (or portion thereof) that is intended to be represented by the composite),
. 13-4 '
-------
FIGURE 13-1
FORMAT FOR THE FIELD ACTIVITIES REPORT
Name of field activities contractor
Address of contractor
Contact Name
. Telephone Number
PROJECT/SITE:
Name
Address
METHODS AND PROCEDURES:
Field Investigation Design: (Reference the sampling plan)
Sample Collection and Handling: (Reference this method)
SAMPLING OBJECTIVES: >
(Complete a brief description here)
SAMPLING LOCATION SELECTION PROCEDURE:
(Complete a brief description here)
Report Title:
Report Number:
Date
SAMPLE DATA
Field
Sample
Number
Location
Identifiers
.
'
Mass of
Sample
.
.
.
'
Mass
Fine
Fraction
. .
Mass
Coarse
' Fraction
Mass
Sample
Split
" .;'
. *
.
. - Mass
Duplicate
Split
.
-
Sample
Split
ID
.-
,'
Duplicate
Split
ID
,
'
V
Date
.Sampled
.' :
Time | Comments:
Sampled |
| (Include Identification
j of all field sampling
\andfieldpr0paratlon
j procedures employed)
-------
An example of the format to be employed for a sample analysis report is presented in Figure
13-2.
13.4 SAMPLE BATCH REPORTS
In addition to the sample analysis report for each sample, provide a summary page for each
batch of samples representing an entire project. The summary sheet shall include: .
(a) the project title;
(b) reference to this method;
(c) the date that samples were collected, the date they were received by the
laboratory, and the date they were analyzed;
(d) a summary listing of sample results including:
the sample number;
the estimated concentration of respirable dust in the sample;
the analytical sensitivity achieved for each size/type category of interest;
the total number of structures of each size/type category of interest counted;
the concentration of asbestos structures of each size/type category of
interest in the sample and in the respirable dust of the sample (both reported
along with corresponding 95% confidence limits); and
the concentration of asbestos structures of each size/type category of
interest estimated for the environmental matrix that was sampled in the field
(reported along with corresponding 95% confidence limits).
An example of the format to be employed for sample batch reports is presented 'in Figure
13-3.
13-7
-------
! FIGURE 13-2
SAMPLE ANALYSIS REPORT FORMAT
Laboratory Name
Laboratory Address
Laboratory Contact
Telephone Number
Date Analysis Started (M/D/Yr) '
Date Analysis Completed (M/D/Yr)
Analyst(s) Initials
Laboratory Sample No.
Field SubSample Identification No.
Field Preparation Technique (Attach a Copy of the Relevant Field Activities Report)
Additional Laboratory Preparation Procedures (describe any employed) '
Sample Drying
Sample Splitting
Other
TEM Analysis: ,
Effective Area of Analytical Filter (sq mm) ,
(Indicate whether from Scrubber or from 1ST Opening)
Magnification , ,
Grid Opening Area (sq mm)
Number of G.O. Scanned
Asbestos Structure Size and Type Categories of Interest (see Chatfield 1993)
Minimum Acceptable Structure Identification Category (see Chatfield 1993)
Dust Generator
Mass of Sample Tumbled (g) i ! '. -
Air Flow Rate Through ME Opening of Dust Generator (ml/min)
Air Flow Rate Through 1ST Opening of Dust Generator (ml/min)
Air Flow Rate Through Scrubber (ml/min) .
Estimated Totat Air Flow Rate Through Elutriator (ml/min)
Total Mass of Dust Collected on Dust Filters (g)
Time of Dust Collection (24 hour clock) at 30 rpm
Start: ..'.'-
Stop: , .
'Time of Dust Collection (24 hour clock) at 60 rpm
Start:
Stop: , ,
Estimated firstorder rate constants-for dust generation (min"1)
At 30 rpm: , -
At 60 rpm:
Estimated Starting Mass of Respirable Dust in Sample (g)
(Attach time plots and calculations)
Samples from the Scrubber Suspension
Total Volume of Scrubber Suspension (ml) '
- Estimated Mass of Dust Collected in Scrubber Suspension (g)
Volume of Aliquot Withdrawn from Scrubber Suspension (ml)
Volume into which Scrubber Aliquot Diluted (ml) -
Dilution Factor (dimensionless) . ,
Volume of Aliquot Filtered (from Diluted .Suspension) (ml)
Samples from the Isokinetic Sampling Tube (1ST) Opening of the Dust Generator .
(indicate whether 30 or 60 rpm run) '
Time of Collection (24 hour clock)
. Start:
: Stop: ',' - ' '
Estimated Mass of Dust Collected on Filter - '
Report Date
Project Name (Optional)
METHODS:'
(reference this method)
Page 1 of 2
-------
FIGURE 13-2
SAMPLE ANALYSIS REPORT FORMAT (Cont.)
Laboratory Name
Laboratory Sample No.
Report Date
Chrysotile Asbestos Analysis Results:
No. of Total Chrysotile Asbestos Structures
No. of Long (> 5 um) Chysotile Asbestos Structures'
No. of Total Chrysotile Asbestos Fibers/Bundles
No. of Long (> 5 um) Chysotile Asbestos Fibers/Bundles
Low
Magnification
High
Magnification
XXX
XXX
Low
Magnification
High
Magnification
Amphibole Asbestos Analysis Results:
No. of Total Amphibole Asbestos Structures XXX
No. of Long (> 5 um) Amphibole Asbestos Structures
No. of Total Amphibole Asbestos Fibers/Bundles XXX
No. of Long (> 5 um) Amphibole Asbestos Fibers/Bundles
(Indicate Amphibole Mineral Type)
ESTIMATED CONCENTRATIONS OF RELEASABLE ASBESTOS IN SAMPLE
. Cone. 95%UCL
Total Chrysotile Structures per g Sample: '
Total Amphibole Structures per g Sample:-
Total Asbestos Structures per g Sample: .
Long Chrysotile Structures per g Sample:
Long Amphibole Structures per g Sample:
Long Asbestos Structures per g Sample:
Estimated Analytical Sensitivity: (structures/g sample)
ESTIMATED CONCENTRATIONS OF RELEASABLE ASBESTOS IN RESPIRABLE DUST OF SAMPLE
Cone. 95%UCL
Total Chrysotile Structures per g Dust:
Total Amphibole Structures per g Dust:
Total Asbestos Structures per g Dust:
Long Chrysotile Structures per g Dust:
Long Amphibole Structures per g Dust:
Long Asbestos Structures per g Dust:
Estimated Analytical Sensitivity: (structures/g dust)
(Attach a Copy of the TEM Raw Data Sheets)
Page 2 of 2
-------
FIGURE 13-3
SAMPLE BATCH REPORT FORMAT
Laboratory Name
'Laboratory Address
Laboratory Contact
Telephone Number
RELEASABLE ASBESTOS.IN-RESPIRABLE DUST
Report Date'
Project Name (Optional)
METHODS:
(reference this method)
Laboratory :
Sample I. D. \Respirable
Dust
Cone
(g/gsmpl)
Total
Asbestos
'.. Analytical
Sensitivity
(s/g dust)
"" '
RELEASABLE ASBESTOS IN LABORATORY SA
Laboratory
Samplel.D. -
RELEASABLE /
Laboratory
Sample!. p,
Respirable
Dust
Cone
. (g/g smpl)
'.
ASBESTOS IN Fl
Field
Samplel.D.
Total
Asbestos
Analytical
Sensitivity
(s/g smpl)
Long
Total , Total Asbestos
Asbestos Asbestos Analytical
. ,Conc 95% UCL Sensitivity
(s/g dust) (s/g dust) (s/g dust)
-': ' '.V '' ' . ' ' '
. - .
:. -" ' ' .-. '.
MPLES - -
Total
Asbestos
Cone
(s/g smpl)
ELD SAMPLE MATRICES
~
Mass
Fine
Fraction
(g)
.
Mass
Coarse
Fraction"
-(g)
Long
Total Asbestos
Asbestos Analytical
95% UCL _ Sensitivity
(s/g smpl) (s/g smpl)
Dust Dust | Comments;
-Long 'Long Generation Generation |
Asbestos Asbestos Rate Rate |
Cone 95%UCL .'(atSOrpm) (at60rpm)|
... (s/g dust) . (s/g dust) "(min'1) (min-1) j
1
"-" ' ': - \ ";
'-.. i
- -, - - i .-
- \ "
Long'
Asbestos
Cone
(s/g smpl)
.';' . I...
Adjusted Adjusted Adjusted
Respirable Total Total
Dust Asbestos Asbestos
: Cone Cone 95% UCL
(g/gmtrx): (s/gmtrx) (s/grritrx)
:.
._ Long
Asbestos
95% UCL
(s/g smpl)
Adjusted
Long
Asbestos
Cone
(s/g mtrx)
Comments: ' " ' . -.
' ''.[..'. ; '
Adjusted | Comments:
Long.
Asbestos
95% UCL . . . .
(s/gmtrx)
-
-------
-------
14.0 REFERENCES
Berman, D.W. and Kolk, A.J. "Performance of a Dust Generator Designed to Support the
Determination of Asbestos in Soils and Bulk Materials." 1994. In Preparation.
Berman, D.W.; Crurrip, K.S.; Chatfield, E.J.; Davis, J.M.G.; and Jones, A. The Sizes, Shapes,
and Mineralogy of Asbestos Structures that Induce Lung Tumors or Mesothelioma in AF/HAN
Rats Following Inhalation." 1995. Risk Analysis 15/2/181 -195.
Berman, D.W. and Chesson, J. "A Superfund Guide: Development of Effective Sampling
Strategies for the Investigation of Asbestos-Related Hazards." USEPA publication, undated.
Under EPA review. .
Berman, D.W.; Kolk, A.J.; Krewer, J.A.; and Corbin, K. "Comparing Two Alternate Methods for
Determining Asbestos in Soils and Bulk Materials." Session-Chair. Session presented at the
Eleventh Annual Conference and Exposition of the Environmental Information Association.
San Diego, March, 1994a.
Berman, D.W.; Kolk, .A.J.; Krewer, J.A.; and Corbin, K. "Pilot Study Results." (1994b)
Unpublished.
Berman, D.W. 'The Search for a Method Suitable for Supporting Risk Assessment: The
Determination of Asbestos in Soils and Bulk Materials, A Feasibility Study." USEPA publica-
tion, 1990. Under EPA review. .
Berman, D.W. and Chatfield, E.J. "Interim Superfund Method for the Determination of
Asbestos in Ambient Air, Part 2: Technical Background Document." USEPA publication
540/2-90/005b, May 1990. :
Chatfield, E.J. "Ambient Air: Determination of Asbestos Fibres, Indirect-Transfer Transmission
Electron Microscopy Procedure." Submitted to: ISO/TC 146/SC 3. 1993.
Chatfield, E.J. and Berman, D.W. "Interim Superfund Method for the Determination of
Asbestos in Ambient Air, Part 1: Method." USEPA publication: 540/2-90/005a, May 1990.
14-1
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' APPENDIX A:
CONSTRUCTION AND OPERATION OF A DUST GENERATOR
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APPENDIX A:
CONSTRUCTION AND OPERATION OF A DUST GENERATOR
FOR ISOLATING THE RESPIRABLE FRACTION OF MATERIAL
FROM SOILS OR OTHER BULK SAMPLES
The dust generator incorporated into this method for the determination of asbestos in soils
and bulk materials is designed to isolate the respirable fraction of material (including the,
releasable fraction of respirable asbestos) that is present within the matrix of the parent
sample. A description of the apparatus is provided below along with a brief discussion of the
theory of its operation. Figures depicting design of the prototype are also provided in the last
section of this appendix to facilitate design and construction of similar equipment.
A.1 DUSt GENERATOR DESCRIPTION
The dust generator is, composed of a tumbler, a vertical elutriator, a dust collection system,
and a scrubber. A schematic diagram of the apparatus is presented in Figure A-1 and a
photograph of the apparatus is shown in Figure;A-2. The appurtenant equipment required to
operate the dust generator is also shown in Figure A-2. This includes: .'
. a DC motor to drive the tumbler; >
a constant humidity chamber to control the humidity of the air that flows into
.the dust generator, This is the clear plastic box enclosing the tumbler in the
photograph;
the pumps required to create an air flow through the dust generator and the
flow controllers required to monitor and apportion air flow through the various
filters and the scrubber; and , ,
the heating mantle, variable voltage transformer, and cooling towers required
for the scrubber. .
A.1.1 The Tumbler
The tumbler is located in the clear plastic enclosure at the bottom of the dust generator
(Figures A-2 and A-3). It is a long shallow tube of square cross section that is approximately
1 and 1/8 inches in height and width and has an overall length of 10 inches (Figure A-4).
The tumbler is driven by a variable speed DC motor, which rotates the tumbler around its
long axis. The tumbler's rotation rate can be varied over the range of 10 to 150 revolutions
per minute (rpm)., The DC motor is attached to,the tumbler using a slip-on type flexible
coupling so that they can be readily detached simply by pulling the motor away from the
tumbler. The tumbler can also be readily detached from the connection tube to the elutriator;
they are connected with a slip fit over the outer race of the ball bearing assembly that is
welded-to the end of the tumbler (Figure A-4). '
A-1
-------
FIGURE A-1
SCHEMATIC OF DUST GENERATOR
To Pumps
Slide Mechanisms
ME Opening From Elutriator
To Scrubber
To DC
Motor
Dust Filter Cassettes
and Mounts
Tumbler
\
\ - 1ST Opening From Elutriator
To Scrubber
* Isokinetic
Sampling
Tube
^Elutriator
Auxilliary Air Inlet
-------
^ Ffov/ - -.1
Contfol Valves -
p.C. Motor-.'/
Controller s
Qonstant '~'
Humidity ;';.
.Chamber / -,}
.--<
D,C;Motor<^ Tumble ' :".
-------
FIGURE A-3
TUMBLER IN CONSTANT HUMIDITY CHAMBER
Front Opening
to Humidity
Chamber
Salt Solution
Trays
D.C, Motor
Friction
Coupling
Air Inlet to
Tumbler
Tumblef
Body
Ball Pearing
Assembly
' Entrance fo
the Eiutrtator ,
-------
-------
NOTE
The seal between the tumbler and elutriator need not be air tight. In fact, a small leak
at this fitting will reduce the chance that particles discharged from the tumbler will
settle in the entrance tube to the elutriator. However, such a leak must not be more
than 10% of the total airflow through the tumbler. ' -
Once the tumbler has been detached from the motor and elutriator, it can simply be lifted out
of the constant humidity chamber.
The top cover of the tumbler is secured with 10 screws and can be removed so that the
tumbler can be loaded or cleaned (Figure A-4). A rubber gasket is employed to assure an
airtight seal between the tumbler cover and body.
A.1.2 The Constant Humidity Chamber
The plastic enclosure that houses the tumbler and isolates it from outside air, except for an
opening at the top front of the enclosure, is designed as a constant humidity chamber
(Figures A-2 and A-3). Air drawn into the front of the enclosure flows successively over two
trays (located on shelves at -the top of the enclosure) before being drawn into the tumbler.
The trays are designed to hold a saturated salt solution that is selected to exhibit a vapor
pressure equal to the relative humidity desired for running the dust generator. The path
length over the two trays is designed to assure that air drawn through the device will come to
equilibrium at a relative humidity within a few percent of the desired value (assuming that the
outside air exhibits a starting humidity within the range common to Pasadena, California1);
the path length must be sufficient to allow adequate exchange of vapor between the salt
solution and the moving air.
For most studies, a relative humidity of approximately 50% should be employed because this
is the humidity at which emission of asbestos is expected to be maximum (Zimon, A.D. 1982).
At higher humidities, air moisture tends to wet surfaces so that aggregation decreases particle
release. At lower humidities, electrostatic effects tend also to cause aggregation and,
therefore, also to decrease emissions. A saturated solution of potassium carbonate dihydrate
is recommended for most applications because such a solution maintains equilibrium with air
at 43% relative humidity at room temperature (20° C) with less than 1% change in humidity
over a range of temperatures varying by several degrees on either side of room temperature.
For special applications of this method, where dust generation is to be run at a different
relative humidity than that produced over a saturated solution of potassium carbonate
dihydrate, the conditioning pans in the dust generator may be filled with a saturated solution
of another, salt. Such salts may be selected to yield any of a broad range of conditions. For
example, the International Critical Tables provides a list of saturated salt solutions that
maintain equilibrium with a broad range of relative humidities in air.
The prototype device was constructed and tested in Pasadena. The design of the constant humidity chamber may
have to be modified slightly (e.g. by increasing the number of trays) for operation in other locale's.
A-6 .
-------
A.1,3 The Vertical Elutriator
The vertical elutriator is the tail metal cylinder visible in Figure A-2. Its dimensions were
selected to assure that the path length traversed by particles in the elutriator. is at least 10
times'the diameter of the elutriator (in the direction perpendicular to the air flow). Thus,
channeling is expected to be minimized (Dennis, R 1976).
The elutriator separates respirable from non-respirable particles and respirable particles are
passed on to dust collection filters and the scrubber. Air flow within the elutriator is adjusted
to a velocity such that only those particles in the respirable size range will be lifted to the top.
The velocity of air selected for the elutriator determines the rate of air flow through all of the
other parts of the dust generator. . , .
The main body of the elutriator is composed of two, 20 in. sections of 4-in. i.d. stainless steel
tubing with a tapered, o-ring flange welded to each end of each tube (Figure A-5a and b).
These flanges allow the two halves of the main body to be connected to each other and to
the top and bottom assemblies of the elutriator using quick-release, pressure clamps (Figure
A-5a). " .. ' ..
The entrance tube to the elutriator (from the tumbler) is pointed downward at its exit point in
the bottom of the elutriator (Figures A-1 and A-5b). This geometry was selected to prevent
introduction of a large concentration of particles into the bottom center of the elutriator. This
geometry should also promote a flatter velocity profile-in the air traveling up the elutriator. It
is expected that respirable particles will make the upward turn because the taper at the
bottom of the elutriator promotes a higher velocity profile at this location than in the main
body of the elutriator (where the air velocity is just sufficient to lift particles in the respirable
size range but no larger).
The bottom assembly of the elutriator has also been designed to allow the removal of coarse
particles while assuring that respirable particles"remain in the elutriator air stream (Figure A-6a
and b)., This is to minimize buildup of a zone at the bottom of the elutriator of a high
concentration of coarse particles through which respirable particles would have to pass
before moving up the elutriator to the dust collection system. Thus, it is expected that
collisions between respirable particles and. coarse particles (with subsequent loss of
respirable particles due to aggregation) are minimized.
An opening at the bottom of the elutriator allows coarse particles to pass into a. removable,
glass cup (Figures A-1 and A-6a and b). . The glass cup has a small side; arm .that is
connected to a two ft. piece of one quarter in. i.d. Tygon tubing. The far end of the Tygon
tube is open to the air- It has been found that, as long the Tygon tube ,is not crimped or
otherwise blocked, air drawn through this tube is just sufficient to prevent respirable particles
from passing through the bottom opening of the dust generator into the glass cup while
allowing larger particles to do so. ,
There are four openings where air may exit from the top assembly of the elutriator (Figures
A-1 and A-7a and b). The two side openings lead into the scrubber (described below). The
two top openings lead into the air filter cassettes of the dust collection system through two
different paths; one draws air isokinetically from the uniform portion of the elutriator through a
long, thin-walled tube and the other draws air from the top, tapered part of the elutriator
(Figures A-1 and A-7a and b). For ease of reference, the opening'in the elutriator that draws
A-7
-------
FIGURE A-5
MAIN BODY OF VERTRICAL ELUTRIATOR
a. Top Section
b. Bottom Section
Body Tube
Quick Release
Pressure Clamp
Entrance Tube1 > BqdyTube
toEfutriator ~ , ~ /<
-------
-------
FIGURE A-7
TOP ASSEMBLY OF VERTICAL ELUTRIATOR
a. Underside View
b. Top View
Side Exits
; (To Scrubber)>
1ST Opening to
\ Elutr&tor,
ME Opening to
Elutfiator v.
,,' ^ "?
,< , f >
' ' Slide M&
ME Opening Isokinetic 1ST Opening
Sampling Tube' -
-------
air through the isokinetic sampling tube is labeled the "1ST1 opening in this document. The
opening that draws air from the top of the main body of the elutriator is labeled the "ME"
opening. The dust collection system mounted over both of the top openings of the elutriator
is described below. ,
A. 1.4 The Dust Collection System
The dust collection system consists of two mounts for filter cassettes welded to each of two
sliding mechanisms, Which in turn are mounted directly over the exit openings of the top
assembly of the vertical elutriator (Figure A-8a and b). An underside view of the tapered top
piece of the elutriator was also shown in Figure A-7a in which the isokinetic sampling tube,is
visible. s - , ; . .
The sliding mechanisms permit the filter cassettes aligned over the ME and the 1ST openings
of the elutriator, respectively, to be changed with minimal disturbance of the air flow; at either
of the two extreme positions in the travel of each slide mechanism, one of the two cassette
mounts-are aligned over the corresponding exit opening of the elutriator and the other is
effectively isolated from the air flow. Details of the sliding mechanisms and filter mounts are
shown in Figures A-7b and A-8a and b.
NOTE
The slides are sealed against the elutriator with b-rings.
periodically for wear and replaced if worn.
These must be inspected
The design of the filter mounts in the dust collection system proved to be important to the
performance of the dust generator; it is critical that these mounts be leak tight. The design
that was ultimately adopted is depicted in Figure A-9a and b. The filter mounts each consist
of a tapered aluminum base that is glued to the bottom half of a commercially available filter
cassette. , . ,
The aluminum base of a filter mount is sealed in each of the openings of the slide
mechanisms with the o-rings that are visible, in Figure A-7b, The bottom half of the plastic,
25 mm filter cassette is glued into the inside taper of the aluminum base. Filters are mounted
in the traditional manner between the top and bottom halves of the plastic filter cassette,
which are then pressure sealed. To further assure a good seal, pressure tape is also applied
to the outside of each filter cassette at the seam where the filters are mounted.
A.1.5 The Scrubber
The scrubber, which can be seen sitting on the table to the right of the main body of the dust
generator in Figure A-2, is constructed from ordinary laboratory glassware. In the scrubber,
water is boiled in the bottom of a 1' liter, round bottom flask (shown seated within a heating
mantle). A straight-jacketed, cold-water condenser is incorporated along the entrance line to
the scrubber and a spiral condenser is incorporated along the exit line from the scrubber. An
immersion pump circulates water between a cooler containing a water-ice mix and .the
condensers. Water - flowing into the condensers is maintained at approximately 0° C. to-
prevent moisture from feaving the.scrubber. . . .... ,
A-11
-------
FIGURE A-8
DUST COLLECTION SYSTEM
a. Side View
b. Top View
Side Exit Opening
of Elutriator
(To Scrubber) >
-------
If.'V " -* ^ i "" f ( "" * ClJ J* * * ^* ft * « ** ^ * "'?,,St~'"jrX4''Cl'%I'\f^V'*' * * }: " A. ' ^XV *> V S ' ^)^ '^rtXS'V!' S
S* ; J " * * ^f f !'x ^> Vn *>£ j. # ? » "" <^ * ? -?1 ^ ft t ^^ -S « y 4 ^ *^ .-^ -0-*- ^ jj ? ^^\ S> NN * ^ \?" > ? *
-------
Particles in the air stream entering the scrubber serve as nucleation centers around which the
steam in .the scrubber condenses. The resulting water droplets eventually fall back into the
water reservoir,at the bottom of the scrubber so that the trapped particles are collected in this
reservoir.
A flowmeter and a filter cassette are also placed in the air flow line that exits-the scrubber
(between the scrubber and the vacuum pump). The primary reason for including the filter
cassette is to make the pressure drop through this path approximately equal to the pressure
drop through the other filter cassettes mounted on top of the elutriator (the dust collection
system). The pressure drop through the elutriator and scrubber is small enough not to affect
the flowmeter operation.
A.1.6 The Configuration of Air Transfer Lines
A schematic indicating the configuration of air transfer lines leading to and from the scrubber
is presented in Figure A-10. As indicated in the figure, the two side exits from the elutriator
are each attached to one ft sections of 1.00 in. i.d. Tygon tubing, which then join at a glass
"Y" connector. The stem end of the "Y" connector is attached (with a one ft section of 1.00 in.
i.d. Tygon tubing) to a diameter reducing piece of glass that feeds into the entrance
condenser to the scrubber through a rubber stopper. The large tubing is held in place at
connections by ring clamps (Figure A-2).
Also as indicated in Figures A-10 and A-2, the exit condenser of the scrubber is connected to
a flow control valve with 0.25 in. i.d. Tygon tubing. The exit side of the flow control valve is
connected first to a 25 mm filter cassette and then to a vacuum pump. Both of these
connections also use 0.25 in. i.d. Tygon tubing.
A schematic indicating the configuration of air transfer lines leading from the filter cassette
mounts of the dust collection system is depicted in Figure A-11. A photograph of the transfer
line connections is also presented in Figure A-12. As indicated in the figures, a 0.25 in. i.d.
Tygon line leads from the exit side of each filter cassette to a plastic, stop cock valve.
Another Tygon line then leads from each valve to one of two plastic "T1 connectors so that
the pair of filter cassettes mounted on the slide mechanism over the 1ST opening of the
elutriator are joined (beyond the stop cock valves) and the pair of filter cassettes mounted on
the slide mechanism over the ME opening are a[so joined (beyond the stop cock valves).
The common line from the exit side of each "T" connector is then connected first to a
flowcontrol valve and then to a vacuum pump. All such connections use 0.025 in. i.d. Tygon
tubing.
NOTE
This is the configuration of air transfer lines that is appropriate during the operation of
the dust generator. The configuration that is appropriate during calibration of air flow
is discussed in Section 9.3.4 of the main text. .
As indicated previously, the side arm on the bottom cup of the elutriator is connected to a
two ft section of 0.25 in. i.d. Tygon tubing that is simply allowed to hang free (Figure A-6a).
A-14
-------
FIGURE A-10
TUBING CONNECTIONS FOR THE SCRUBBER
OF THE DUST GENERATOR
I To Pumps
For Detail
, See Fig. A-11
To DC
Motor
Tumbler
Flow Rate Meter
(-1200 ml/min)
Valves Closed
For Initial
Calibration
To Precision
Control Valve
and Vacuum Pump
_ Auxiliary Air Inlet
(Always Open)
25mm Filter
Cassette
With Stopper
and 1/4" Metal
Tube
Stop Cock Valves
-------
FIGURE A-11
TUBING CONNECTIONS FOR FILTER CASSETTES
MOUNTED ON THE ELUTRIATOR OF THE DUST GENERATOR
ME Opening From Eluatriator
Slide Mechanisms on the
Top of the Elutriator
Top of the Elutriator
1ST Opening From Elutriator
Isokinetic Sampling Tube
To Precision Control Valve
and Vacuum Pump
Stop Cock Valves
-------
V .* ' ^ *«2i % ^^^^^^^^^^^j^^**^^*^^^
-------
A.2 THEORY OF OPERATION
A.2.1 The Dynamics of Dust Generation
The dynamics of the release of dust from a sample during a run using the dust generator
have been evaluated so that the rate of release and mass of dust in the sample can be
derived from measurements of the mass of dust deposited over time on the set of filters
collected over the ME opening of the elutriator. Analysis of data obtained from several
different types of samples during the pilot study for this method (Berman et al., 1994)
indicate that the rate of release of mass from a sample in the dust generator is well described
by a first-order rate equation: - .
where:
t
k
= k*M
(A-1)
is the mass of respirabie dust remaining in the sample at time "t"
(g);
is the time since the start of the run (s); and
is the first-order rate constant for the release (s"1).
The minus sign in this equation indicates that mass is lost-with time.
Equation A-1 can be integrated to yield:
ln(Ms) = ln(M0) - kt
(A-2)
where:
M0 is the mass of respirabie dust in the sample at the start of the
run (i.e. at time t = 0) (g).
Given that "Ms" can also be expressed as the difference between "M0" and "Mr" the cumulative
mass released up to time "t," Equation A-2 can also be expressed as:
ln(M0 - Mr) = ln(M0) -kt
(A-3)
where:
Mr is the cumulative mass released between the start of a run and
. ' time T (g).
The relationship presented in Equation A-3 indicates that a plot of the natural logarithm of the
quantity (M0 -Mr) versus time should be a straight line with a slope equal to the rate constant
for dust release, k, and an intercept equal to the initial mass of dust in the sample at the start
A-18
-------
of the run, M0. The cumulative mass of dust released from the sample over time, Mr, can be
,.derived from measurements of dust collected on filters during the run! However, because M0
also appears as part of one of the parameters that must be plotted to evaluate the
relationship expressed in Equation A-3, the value of M0 must be optimized using regression,
as described in Section 11.2 of the main text of this method.
The cumulative mass released from a sample at time "t" during a run, "Mr" is directly
proportional to the cumulative mass measured on filters collected during the run:
M, = Mf*(Fs + Fd + FC)/FC
where:
(A-4)
s
is the cumulative mass measured on filters collected from filters
mounted over the top of the elutriator up to time "t" (g);
is the rate of airflow through the scrubber (cm3/s);
is the rate of airflow through the 1ST opening of the elutriator
(cm3/s); and . "
rc is the rate of airflow through the ME opening of the elutriator
(cm3/s).
Because Fs and Fc will typically have been set to 0.48*VV and Fd will typically have been set
to 0.047*VV during the initial setup of the dust generator (see Section 9.3.4), for most
applications, Equation A-4 reduces to: / . ,
Mr = 2.1 *Mf
(A-5)
As indicated above, values for MQ must be derived by performing a regression analysis of the
relationship described by Equation A-3. This can be accomplished by using any of several
commercially' available spreadsheet programs (such as, for example, LOTUS). The
procedure to be followed to derive estimates of M0 and k are described in Section 11.2.
A.2.2 The Time Dependence of Dust Collection
As indicated in Section A.2.1 above, the generation of dust from the tumbler is well described
by the first order rate equation: ;
-dMs/dt = k
(A-1)
However, experience gained during the-pilot study for this method (Berman et al. 1994)
further indicates that the rate of change of Ms is sufficiently slow in most cases such that, for
periods of no more than 5 to 10 minutes, Ms can be considered constant. Thus, for
A-19
-------
estimating such things as the time required to load individual filters in the dust generator, a
simpler form of Equation A-1 can be used (in which Ms is considered constant):
where:
A Ms = k*Ms*At
(A-6)
Ms is still the mass of respirable dust remaining in the sample at
time "t" but it is assumed constant over the short interval of time
"At"(g);
A Ms is the mass of respirable dust released from the sample over the
short time interval "At" (g);
At is a relatively short time interval (no more than ten minutes)
during which the release of dust is being estimated (s); and
is still the first-order rate constant for the release (s"1).
Based on Equation A-6, the mass of respirable dust deposited on a filter in the dust
generator, call this AMf, is simply the product of the dust released from the sample, AMS, and
the fraction of the flow through the dust generator that is also directed through that filter.
Thus, for filters collected over the isokinetic sampling tube (the 1ST opening of the elutriator):
AMf = 0.047* k*Ms*At
or for filters collected over the ME opening of the elutriator:
(A-7)'
AM, = 0.48* k*Ms*At
(A-8)
The correct value for Ms to be used with Equations A-7 and A-8 is the value estimated by the
relationship provided in Equation A-2 of Section A.2.1 where the "t" In Equation A-2 is the
time that has elapsed from the beginning of the run to the start of the interval of interest, "At".
NOTE
In deriving Equations A-7 and A-8, it was assumed that air flow within the dust
generator was setup as described in Section 9.3.4.
A-20
-------
A.2.3 Size Separation Using the Vertical Elutriator
Separation of the respirable fraction of a paniculate matrix can be accomplished by exploiting
differences in the settling velocities of particles of different sizes when such particles are
suspended in either a liquid or gaseous medium. However, air was selected as the medium
into which samples would be suspended in this method to avoid changes in the
characteristics of asbestos that typically occur when asbestos samples are placed in water2.
The force on a particle suspended in a moving fluid is given by Stake's Law (Fuchs, N.A.
1964). When such a particle is suspended in a fluid that is moving upward such that the
force of the fluid and the force of gravity on the particle just balance and the particle remains
motionless, Stake's Law indicates that the following relationship holds:
4/3**:*r3*d*g = -6*jt*n
(A-9)
where:
r is the radius of the particle (cm);
d is the density of the particle (g/cm3); '
g is .the acceleration due to gravity (cm/s2);
T) is the dynamic viscosity of the fluid (g/cm*s); and
V| is the linear velocity of the fluid (cm/s).
The velocity estimated in Equation A-9 is termed the Stake's velocity, Vs.
By substituting the viscosity of air at room temperature (i.e. 20° C) and the acceleration due
to gravity into Equation A-9, the value of the Stake's velocity of a particle is estimated as
follows: ' ' '.-,'
Vs =
(A-10)
where Vis -the radius of the particle and "d" is the density of the particle. Because respirable
particles are generally defined as those exhibiting an "aerodynamic equivalent diameter" of
10 urn, where an aerodynamic equivalent diameter is the diameter of a particle of unit density
that settles at the same rate as the particle of interest, Equation A-10 can be used to find the
Stake's velocity of the largest respirable particles in the elutriator (i.e. by substituting a radius
of 5 |im and assuming a density of 1):
V. = 0.295 cm/s
It is well documented that the size distribution of' asbestos structures in a sample change when such a sample is
placed in water. For an overview of such documentation, see Berman and Chatfield (1990). Typically, the number of
small fibers and bundles increases and the number and complexity of clusters and matrices decrease when asbestos
samples are placed in water. . '
. A-21 .''.-'
-------
The Stake's velocity for a particle is also equal to the veiocity of the fluid stream that will just
hold a particle motionless against gravity. Because the goal of the dust generator is to
capture all particles that are potentially respirable, the velocity of air within the elutriator
should be set so that it is just slightly larger (i.e. by 5%) than the Stake's velocity estimated
above (for the largest respirabie particles) so that all respirable particles.entering the elutriator
will be imparted with an upward velocity and will be carried along with the air stream so that
they are, ultimately, either deposited on a filter or passed into the scrubber. therefore,
airflow within the dust generator should be set so that the velocity of air within the vertical
elutriator is 5% greater than 0.295:
V( = 0.31 cm/s.
A.3 DUST GENERATOR PROTOTYPE DESIGN FIGURES AND CONSTRUCTION
GUIDELINES
The figures of the prototype dust generator that are included in this package are intended to
be suggestive and not meant to be followed in exact detail. However, the dimensions of the
various cross-sectional areas of different parts of the dust generator, which affect the relative
air flows in various places, need to be followed closely for the dust generator to perform as
intended. Other design features, such as couplings, clamps, and seals are intended more to
be illustrative; alternate designs can be equally effective.
In spite of the low pressure differentials developed during operation in the prototype,
performance was found to be very sensitive to leaks, especially leaks occurring in the
isokinetic sampler filter mounts. Design features associated with the dust collection system
should therefore be selected so as to minimize the potential for leaks in this area. The air
flow path in the elutriator of any dust generator that is constructed for use with this method
should be tested for leaks when construction is completed and periodically thereafter.
So that dust generator equipment constructed for use with this method will perform
adequately, the following requirements must be incorporated into its design:
the tumbler must be designed to hold a minimum of approximately 100 g of
sample (with ample space left over to allow adequate tumbling) so that field
homogenization requirements are not compromised. It should also be
designed to assure a reasonably long pathlength over which air passes
through the sample and baffles (or square corners) should be incorporated to
assure adequate tumbling action and thorough mixing of sample and air;
the pathlength of the elutriator should be a minimum of 10 times its diameter to
minimize the possibility of channeling and the diameter should be large enough
to assure a cross-sectional area that is at least 10 times that of the tumbler.
This latter requirement is to assure adequate air flow in the tumbler that will
effect efficient transfer of sample while flow throughout the device is limited to
allow flow in the elutriator to be set at 1.05 times the settling velocity of the
largest respirable particle of interest; . '
A-22
-------
the entrance tube and bottom of the elutriator should be shaped so that
. sufficient air velocities are maintained in this part of the device to assure a
smooth, transition (with efficient sample transfer), between flow in the tumbler
and flow in the elutriator. It is also recommended that the entrance tube to the
elutriator be pointed downward as a further, hindrance to channeling in the
^ elutriator; and
filter mounts in the dust collection system need to allow for ready, facile
exchange of filters while minimizing the potential for air leaks in this area. A
modification incorporated into the prototype device to achieve both
requirements was to design aluminum mounts that are tapered such that the
shaved bottom half of commercially available filter cassettes fit snugly and can
-be glued in place (to prevent air leaks at this joint). These can then be fitted
with filters and joined to the matching top halves of commercially available
cassettes. This feature takes good advantage of the fit between the two plastic
halves of a commercial filter cassette, which are designed to join with minimal
leakage while allowing for rapid exchange of filters. The bottom half of the
aluminum filter mounts are sealed" into the slide mechanisms on the prototype
apparatus with o-rihgs.
The following figures are included in this package: , , ,
» Figure A-13 indicates the overall assembly of the prototype dust generator;
Figure A-14 indicates the details of the prototype tumbler assembly;
, Figure A-15 indicates the details of the prototype vertical elutriator;
, Figure A-16 is a vertical cross-section of the top of the prototype vertical
elutriator indicating the relationship between the elutriator openings, the
isokinetic sampling tube, and the slide mechanisms of the dust collection
system;
Figure A-17 indicates the, details of the isokinetic sampling tube;
Figure A-18 indicates the details of the prototype slide mechanism of the dust
collection assembly; and ,-.,.'.
. Figure A-19 indicates the details of the prototype filter cassette mounts. '
A-23
-------
-------
FIGURE A-13 OVERALL PROTOTYPE DUST GENERATOR ASSEMBLY
10
12
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LIST:
A. 1' SO, SIBEL TUBE
B. 1* X .25' STEEL STRAP
C. .0625 ALUMINUM SHROUD
D. SPEED CONTROLLER (0-150rpm)
E. DC-MOTOR(O.-JSOrpm)
F. MOTOR MOUNTS :
G. MOTOR PWTE
REAR' END VIET
fl. PIPE ASSEMBLY
I. FLOW METERS
J. HUMIDITY CONTROLLED PLASTIC ENCLOSURE
K.: ALUMINUM SHAFT IT/COUPLINGS
L SAMPLE CHAMBER '
M. SEALED BEARING
N.-SPRING HOLDERS
-------
FIGURE A-14 PROTOTYPE TUMBLER ASSEMBLY DETAIL
10
12
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FOR AIR FLOW
TOP VIEff
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O L^ O O O JO
NOTE: Use 10-32 SHCS
L.2SO OIA. HOLE FOR AIR FLOW
CUT AWAY FOR CLARITY
.0625 S.S. FLANGED PLATE
SEALED BEAKING
ALUMINUM END PLUG #1
1.250.X .0625 S.S. SQ. TUBE
ALUMINUM END PLUG J2 ^
SPIDER COUPLING
00.8750
RUBBER GASKET
S.S. COVER PLATE
0 2.1250
SIDE VIEff
END VIEF
AOSC (MUSS OJHOtttSf SlfVfXZ
00 HOT SOU MUttZ
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FIGURE A-15 PRU1UI
HOC Mas omma smm
ca tor sou w**t
.TOP SLIDE ASSEMBLY
CASKET
SECTION 1
SEE DETAIL A
- 0-R.ING
20.5625
SECTION 2
4.00 DIA. X .0625 ffAE
S.S. RD. TUBING
0-RINC
20.^625.
13.000
SECTION 3
4.00 DIA. X .0625
S.S. RD. TUBING
-1.50 DIA. X .0625 ffAU
S.S. RD. TUBING
0-RING
SECTION-4
1.50 DIA. X .0625 1TALL
S.S. RD. TUBING
GLASS CONTAINER
fflTH RUBBER SEA,',
10
NOTE: S.ections joined together -
by pivot damps.
AH screws are 10-32 SHCS
p ; '»»«»« -jol
I / L 1.060 x .03 si »: - / \ ! .
U .""./ U'
nwtvnr
-tins
MATERIAL: STAINLESS STEEL
DETAIL A
12
10
12-
A''
-------
FIGURE A-16
SECTION OF ELUTRIATOR TOP
WITH EXTENSION TUBE
i
'///I '//* I - Ob
W////////////////////////I
I
CL
GL
-------
FIGURE A-17
LONGITUDINAL & TRANSVERSE SECTIONS OF
ISOKJNETIC SAMPLING TUBE
8.
>
t
t
6.3
5"
\
/
1.-
r >
''"'' ^
' * ^
s
\
x
' *
X
\
X
X
\
S
S
X
s
X
X
X
X
s
N
X
N
X
. . s
X
X
X
X,
0
' - \
X
X
X
75" ' \
X
X
X
\
s,
X,
X
N
X
X
\
X
X
X
\
N
X
N
\
\
. \
\
N
: \
A
\
\
X
N
o
\
X
. \
^
v\
X
/ ' -I
X
\ ' 1
A
.. A
75" .
r ,
V
V
0
0
V
V
\
^
V
\
\ "
0
0
Xs
0
v;
x
V
S
C
C
\ -
0
0
\
X
X
s
X '
0
c
\
^
V
X
c
X . .
X
c
c
X
s
v
s
x
X
X
V "
\
s
\
\.
\
\ .
\
r
\
\
s
V
\
c .
\
\
V
\
\ -
V
\
\
\ -
\
\
\
\
V
\
\
c
c
\ .
V
!;
\
c
x
x
\
\
0 .
c
X. __i
\
\
c
c
\
c
\
1
)
(
/ 78.3°
1' ' A1
^ v .
X
X
X
X
X
X
/ -
/ 87.3°
SCALE 1"=,1" ^L
\\
I/
«E ' 0:87"-
-0.905"-
1.06"-
AA1
SCALE x2
-------
FIGURE A-18 PHOTOTYPE SUDE MECHANISM DETAIL
10
12
r.
0,0
O ' 0
TOP VOT
SLIDER BLOCK jl
SLIDER SI
GUIDE RAIL jl
BASE PLATE
CENTER GUIDE RAIL
SLIDER #2
SLIDER BLOCK #2
GUIDE RAIL #2
Zin- CENTER GUIDE RAIL
1 I
GUIDE RAIL #2
r
W
i
urn
r-U4
<* p «^
SLIDER #2 GUIDE RAIL #2
||_[ SLIDER BLOCK #2
BASE PLATE
CENTER GUIDE RAIL
GUIDE RAIL #1 -C?I '!
SLIDER BLOCK #2 ! I \
GASKET SLIDER BLOCK #1
GASKET : !
lOOOO-
SIDE WEff
SLIDER #2
- 0-RINGS
BASE PLATE
SLIDER #1
0-RINCS
CENTER GUIDE JttIL
GUIDE RAIL #2
SLIDER BLOCK #2
GASKET
SLIDER #2
0-RINGS
BASE PLATE
END WE₯
TOP SLIDE-ASSEMBLY
MATERIAL: ALUMINUM
-------
FIGURE A-19
DETAIL OF PROTOTYPE FILTER CASSETTE MOUNTS
Radius Corner
23.6mm
".930 in.
23 mm
.905 in.
/.
2 Degree
Included Angle
\^___
. .
1
i
i
ALUMINUM CASSETTE HOLDER, TOP MODIFIED WITH INTERNAL TAPER AS SHOWN
Radius Corner
I
1
>
rf 20mm k
.787 in.
* \
t ^
23mm f Degree
905 in Included Angle
r j
25MM MILLIPORE CASSETTE, BOTTOM MODIFIED WITH EXTERNAL TAPER AS SHOWN
CASSETTE AND HOLDER SHOWN JOINED TO CREATE A TAPER LOCK SEAL
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-------
REFERENCES
Berman, D.W.; Kolk, A.J.; Krewer, J.A.; and Corbin, K. "Comparing Two Alternate Methods for
. Determining Asbestos in Soils and Bulk Materials." Session Chair. Session presented at the
Eleventh Annual Conference and Exposition of the Environmental Information Association.
San Diego, March, 1994. '
Berman, D.W. and Chatfield, E.J. "Interim Superfund Method for the Determination of
Asbestos in Ambient Air, Part 2: Technical Background Document." USEPA publication:
540/2-90/005b, May 1990.
s \, .' _ . ."'"''-.,
Dennis, R. (ed.) Handbook on Aerosols. Reprinted by the Technical Information Center. U.S.
Department of Energy. NTIS No. TID-26608. 1976.
Fuchs, N.A. The Mechanisms of Aerodols. Oxford: Pergamon Press, N.Y. 1964. Translation
of: Mekhanika Aerozolei. '
Zimon, A.D. Adhesion of Dust and Powder (2nd Ed.) Constants Bureau, N.Y. 1982.
Translated from Russian by R.K. Johnston.
A-31
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