ASTM D7201-06(2020)

Standard Practice for Sampling and Counting Airborne Fibers, Including Asbestos Fibers, in the Workplace, by Phase Contrast Microscopy (with an Option of Transmission Electron Microscopy)

SIGNIFICANCE AND USE
5.1 Users of this practice must determine for themselves whether the practices described meet the requirements of local or national authorities regulating asbestos or other fibrous hazards.  
5.2 Variations of this practice have been described by the Asbestos Research Council in Great Britain (8), the Asbestos International Association (AIA) RTM 1 (9), NIOSH 7400, OSHA ID 160, and ISO 8672. Where the counting rules of the latter three methods differ, this is noted in the text.  
5.3 Advantages:  
5.3.1 The technique is specific for fibers. PCM is a fiber counting technique that excludes non-fibrous particles from the analysis.  
5.3.2 The technique is inexpensive, but requires specialized knowledge to carry out the analysis for total fiber counts, at least in so far as the analyst is often required under regulations to have taken a specific training course (for example, NIOSH 582, or equivalent).  
5.3.3 The analysis is quick and can be performed on-site for rapid determination of the concentrations of airborne fibers.  
5.4 Limitations:  
5.4.1 The main limitation of PCM is that fibers are not identified. All fibers within the specified dimensional range are counted. Differential fiber counting may sometimes be used to discriminate between asbestos fibers and fibers of obviously different morphology, such as cellulose and glass fiber. In most situations, differential fiber counting cannot be used to adequately differentiate asbestos from non-asbestos fibers for purposes of compliance with regulations without additional positive identification. If positive identification of asbestos is required, this must be performed by polarized light or electron microscopy techniques, using a different portion of the filter.  
5.4.2 A further limitation is that the smallest fibers visible by PCM are about 0.2 μm in diameter, while the finest asbestos fibers may be as small as 0.02 μm in diameter.  
5.4.3 Where calculation of fiber concentration provides a result exceed...
SCOPE
1.1 This practice2 describes the determination of the concentration of fibers, expressed as the number of such fibers per millilitre of air, using phase contrast microscopy and optionally transmission electron microscopy to evaluate particulate material collected on a membrane filter in the breathing zone of an individual or by area sampling in a specific location. This practice is based on the core procedures provided in the International Organization for Standardization (ISO) Standard ISO 8672  (1),3 the National Institute for Occupational and Health (NIOSH) Manual of Analytical Methods, NIOSH 7400  (2), and the Occupational Safety and Health Administration (OSHA) ID 160  (3). This practice indicates the important points where these methods differ, and provides information regarding the differences, which will allow the user to select the most appropriate procedure for a particular application. However, selecting portions of procedures from different published methods generally requires a user to report that they have used a modification to a method rather than claim they have used the method as written.  
1.2 The practice is used for routine determination of an index of occupational exposure to airborne fibers in workplaces. Workplaces are considered those places where workers are exposed to airborne fibers including asbestos. Additional information on sampling strategies, sample collection (including calibration) and use of sample results for asbestos abatement projects is provided in a standard Practice for Air Monitoring for Management of Asbestos-Containing Materials (WK 8951) currently being considered by ASTM subcommittee E06.24. A further practice has been approved for the specific purpose of sampling and counting airborne fibers in mines and quarries (Practice D7200), although the practice herein may also be used for this purpose. The current practice may be used as a means of monitoring occupational exposure...

General Information

• Status: Published
• Publication Date: 14-Apr-2020
• ICS: 13.040.30 - Workplace atmospheres
• Technical Committee: D22 - Air Quality
• Drafting Committee: D22.07 - Sampling, Analysis, Management of Asbestos, and Other Microscopic Particles

Relations

• Replaces: ASTM D7201-06(2011) - Standard Practice for Sampling and Counting Airborne Fibers, Including Asbestos Fibers, in the Workplace, by Phase Contrast Microscopy (with an Option of Transmission Electron Microscopy)
• Effective Date: 15-Apr-2020
• Refers: ASTM D1356-20a - Standard Terminology Relating to Sampling and Analysis of Atmospheres
• Effective Date: 01-Sep-2020
• Refers: ASTM D1356-20 - Standard Terminology Relating to Sampling and Analysis of Atmospheres
• Effective Date: 15-Mar-2020
• Refers: ASTM D1357-95(2019) - Standard Practice for Planning the Sampling of the Ambient Atmosphere
• Effective Date: 01-Aug-2019
• Refers: ASTM D6620-19 - Standard Practice for Asbestos Detection Limit Based on Counts
• Effective Date: 01-Jan-2019
• Refers: ASTM D1356-15a - Standard Terminology Relating to Sampling and Analysis of Atmospheres
• Effective Date: 15-Oct-2015
• Refers: ASTM D1356-15 - Standard Terminology Relating to Sampling and Analysis of Atmospheres
• Effective Date: 01-Jul-2015
• Refers: ASTM D1356-14b - Standard Terminology Relating to Sampling and Analysis of Atmospheres
• Effective Date: 01-Dec-2014
• Refers: ASTM D1356-14a - Standard Terminology Relating to Sampling and Analysis of Atmospheres
• Effective Date: 01-May-2014
• Refers: ASTM D1356-14 - Standard Terminology Relating to Sampling and Analysis of Atmospheres
• Effective Date: 15-Jan-2014
• Refers: ASTM D5337-11 - Standard Practice for Flow Rate for Calibration of Personal Sampling Pumps
• Effective Date: 15-Nov-2011
• Refers: ASTM D1357-95(2011) - Standard Practice for Planning the Sampling of the Ambient Atmosphere
• Effective Date: 01-Oct-2011
• Refers: ASTM D6620-06(2010) - Standard Practice for Asbestos Detection Limit Based on Counts
• Effective Date: 01-Oct-2010
• Refers: ASTM D1356-05(2010) - Standard Terminology Relating to Sampling and Analysis of Atmospheres
• Effective Date: 01-Apr-2010
• Refers: ASTM D6281-09 - Standard Test Method for Airborne Asbestos Concentration in Ambient and Indoor Atmospheres as Determined by Transmission Electron Microscopy Direct Transfer (TEM)
• Effective Date: 01-Dec-2009

Overview

ASTM D7201-06(2020), titled Standard Practice for Sampling and Counting Airborne Fibers, Including Asbestos Fibers, in the Workplace, by Phase Contrast Microscopy (with an Option of Transmission Electron Microscopy), is a key international standard developed by ASTM. This practice outlines reliable procedures for determining the concentration of airborne fibers-including asbestos-in workplace environments using phase contrast microscopy (PCM), with an optional addition of transmission electron microscopy (TEM) for enhanced analysis. The standard is widely referenced for occupational exposure monitoring and regulatory compliance in environments where workers may be exposed to fibrous particulates.

Key Topics

• Scope and Methods: The standard details the process for sampling air in workplace or specific area locations, collecting particulate matter on membrane filters, and analyzing fiber concentrations using PCM. It offers an option for TEM where further fiber identification is necessary.
• Comparison to Other Methods: ASTM D7201 draws on internationally recognized methods, referencing ISO 8672, NIOSH 7400, and OSHA ID 160. The practice discusses the key differences between these approaches, helping users select the most suitable method for their needs.
• Advantages:
  • PCM is cost-effective and can provide rapid, on-site determination of airborne fiber concentrations.
  • The technique is fiber-specific, excluding non-fibrous particles from results.
• Limitations:
  • PCM cannot independently identify fiber types; all fibers within specified dimensions are counted, regardless of their origin.
  • The smallest fibers detectable by PCM are approximately 0.2 μm in diameter, so finer fibers, such as some asbestos varieties, may not be fully accounted for.
  • Additional microscopy (such as polarized light or TEM) is required for positive asbestos identification when regulatory compliance mandates fiber type differentiation.

Applications

• Occupational Safety and Health: Primarily used to assess worker exposure to airborne fibers, including asbestos and other mineral fibers, in industries such as construction, manufacturing, and mining.
• Area Monitoring: Can be used for area samples to evaluate fiber concentrations in indoor environments, aiding in risk assessments and asbestos management programs.
• Asbestos Abatement Projects: Results from fiber counting can guide the effectiveness of asbestos removal or containment efforts and help ensure regulatory requirements for air clearance are met.
• Air Quality Compliance: Allows employers and facility operators to monitor fiber concentrations and demonstrate compliance with occupational exposure limits as required by local or national authorities.
• Special Environments: While tailored to occupational settings, this practice may also be applied in mines, quarries, and other unique environments where airborne fibrous hazards are present.

Related Standards

• ISO 8672: International standard for air quality assessment of airborne asbestos fibers by PCM.
• NIOSH 7400: Method for fiber counting using PCM, frequently cited in occupational health.
• OSHA ID 160: Regulatory method for testing airborne fibers, including asbestos, in workplace environments.
• ASTM D7200: Specific practice for sampling and counting airborne fibers in mines and quarries.
• ASTM D1356, D5337, D6620: Supporting standards for air quality terminology, sampling pump calibration, and limit of detection procedures.

Practical Value

Implementing ASTM D7201 enables organizations to systematically monitor airborne fibers, safeguard worker health, and comply with regulatory obligations. The flexibility to reference or combine internationally recognized methods makes this standard a practical and authoritative resource for industrial hygienists, safety managers, and environmental consultants focused on fiber hazard management.

Keywords: ASTM D7201, airborne fibers, asbestos monitoring, workplace air quality, phase contrast microscopy, transmission electron microscopy, fiber counting, occupational exposure, air sampling, fiber safety compliance.

Standards Content (Sample)

This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: D7201 − 06 (Reapproved 2020)
Standard Practice for
Sampling and Counting Airborne Fibers, Including Asbestos
Fibers, in the Workplace, by Phase Contrast Microscopy
(with an Option of Transmission Electron Microscopy)
This standard is issued under the fixed designation D7201; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope tee E06.24. A further practice has been approved for the
specific purpose of sampling and counting airborne fibers in
1.1 This practice describes the determination of the con-
mines and quarries (Practice D7200), although the practice
centration of fibers, expressed as the number of such fibers per
herein may also be used for this purpose. The current practice
millilitreofair,usingphasecontrastmicroscopyandoptionally
may be used as a means of monitoring occupational exposure
transmission electron microscopy to evaluate particulate mate-
toasbestosfiberswhenasbestosfibersareknown a prioritobe
rial collected on a membrane filter in the breathing zone of an
present in the airborne dust. The practice gives an index of
individual or by area sampling in a specific location. This
airborne fiber concentration. This practice may be used in
practice is based on the core procedures provided in the
conjunction with electron microscopy (see Appendix X1) for
International Organization for Standardization (ISO) Standard
assistance in identification of fibers.This practice may be used
ISO 8672 (1), the National Institute for Occupational and
for other materials such as fibrous glass, or man-made mineral
Health (NIOSH) Manual ofAnalytical Methods, NIOSH 7400
fibers by using alternate counting rules (see Annex A4).
(2), and the Occupational Safety and Health Administration
(OSHA) ID160 (3). This practice indicates the important
1.3 Thispracticespecifiestheequipmentandproceduresfor
points where these methods differ, and provides information
samplingtheatmosphereinthebreathingzoneofanindividual
regarding the differences, which will allow the user to select
and for determining the number of fibers accumulated on a
the most appropriate procedure for a particular application.
filter membrane during the course of an appropriately-selected
However, selecting portions of procedures from different
sampling period. The practice may also be used to sample the
published methods generally requires a user to report that they
atmosphere in a specific location or room of a building (area
have used a modification to a method rather than claim they
sampling), where this may be helpful in assessing exposure to
have used the method as written.
workers handling fiber-containing products.
1.2 The practice is used for routine determination of an
1.4 The ideal working range of this test practice extends
index of occupational exposure to airborne fibers in work-
2 2
from 100 fibers/mm to 1300 fibers/mm of filter area. For a
places. Workplaces are considered those places where workers
1000-L air sample, this corresponds to a concentration range
are exposed to airborne fibers including asbestos. Additional
information on sampling strategies, sample collection (includ- from approximately 0.04 to 0.5 fiber/mL(or fiber/cm ). Lower
and higher ranges of fiber concentration can be measured by
ing calibration) and use of sample results for asbestos abate-
ment projects is provided in a standard Practice for Air reducing or increasing the volume of air collected. However,
Monitoring for Management ofAsbestos-Containing Materials whenthispracticeisappliedtosamplingthepresenceofother,
(WK 8951) currently being considered by ASTM subcommit-
non-asbestos dust, the level of total suspended particulate may
impose an upper limit to the volume of air that can be sampled
if the filters produced are to be of appropriate fiber loading for
fiber counting.
ThispracticeisunderthejurisdictionofASTMCommitteeD22onAirQuality
and is the direct responsibility of Subcommittee D22.07 on Sampling, Analysis,
1.5 Users should determine their own limit of detection
Management of Asbestos, and Other Microscopic Particles.
Current edition approved April 15, 2020. Published April 2020. Originally
using the procedure in Practice D6620. For Reference the
approved in 2006. Last previous edition approved in 2011 as D7201–06 (2011).
NIOSH 7400 method gives the limit of detection as 7 fibers/
DOI: 10.1520/D7201-06R20.
2 mm offilterarea.Fora1000Lairsample,thiscorrespondsto
This practice is based on NIOSH 7400, OSHAID160, and ISO 8672. Users of
this ASTM standard are cautioned that if they wish to comply with one of these
a limit of detection of 0.0027 fiber/mL (or fiber/cm ). For
specificproceduresexactlytheyshouldfollowthatprocedure,otherwisetheyshould
OSHAID160 the limit of detection is given as 5.5 fibers/mm
document the modification
3 of filter area. For a 1000 L air sample, this corresponds to a
The boldface numbers in parentheses refer to a list of references at the end of
this standard. limit of detection of 0.0022 fiber/mL (or fiber/cm ).
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D7201 − 06 (2020)
1.6 If this practice yields a fiber concentration that does not 2.2 Other Standards:
exceed the occupational limit value for the particular regulated NIOSH 7400National Institute for Occupational Health and
fiber variety, no further action may be necessary. If the fiber Safety (NIOSH), (Revised 1994)
concentration exceeds the occupational limit value for a Recommended Technical Method No.1 (RTM 1)Asbestos
International Association (AIA)
specific fiber variety, and there is reason to suspect that the
specific fiber variety is mixed with other fibers not covered ID 160 Occupational Safety and Health Administration
(OSHA)
under the same standard or regulation, the optional method
specified in Appendix X1 may be used to measure the ISO 8672International Organization for Standardization
(ISO)
concentrationorproportionofthefiberscountedthatareofthe
regulated variety.
3. Terminology
1.7 The mounting medium used in this practice has a
3.1 Description of Terms Specific to This Standard—In
refractive index of approximately 1.45. Fibers with refractive
addition to those found in Terminology D1356:
indices in the range of 1.4 to 1.5 will exhibit reduced contrast,
3.1.1 area sample, n—an air sample collected so as to
and may be difficult to detect.
representtheconcentrationofairbornedustinaspecificareaor
room, which, in the case of this practice, refers to an area or
1.8 Fibers less than approximately 0.2 µm in diameter will
room of a workplace.
not be detected by this practice (4).
3.1.2 asbestiform, n—a specific type of fibrous mineral
1.9 The values stated in SI units are to be regarded as
growth habit in which the fibers and fibrils exhibit a polyfila-
standard. No other units of measurement are included in this
mentous growth habit and possess high tensile strength and
standard.
flexibility. All materials regulated as asbestos are asbestiform,
1.10 This standard does not purport to address all of the
but not all asbestiform minerals are classified as asbestos.
safety concerns, if any, associated with its use. It is the
Characteristicssuchastensilestrengthandflexibilitycannotbe
responsibility of the user of this standard to establish appro-
ascertained from microscopic evaluation.
priate safety, health, and environmental practices and deter-
3.1.3 asbestos, n—a term applied to six specific silicate
mine the applicability of regulatory limitations prior to use.
minerals belonging to the serpentine and amphibole groups,
For specific precautionary statements, see Section 7.
which have crystallized in the asbestiform habit, causing them
1.11 This international standard was developed in accor-
to be easily separated into long, thin, flexible, strong fibers
dance with internationally recognized principles on standard-
when crushed or processed (5). The Chemical Abstracts
ization established in the Decision on Principles for the
Service Registry Numbers of the most common asbestos
Development of International Standards, Guides and Recom-
varieties are: chrysotile (12001-29-5), riebeckite asbestos (cro-
mendations issued by the World Trade Organization Technical
cidolite) (12001-28-4), grunerite asbestos (Amosite) (12172-
Barriers to Trade (TBT) Committee.
73-5), anthophyllite asbestos (77536-67-5), tremolite asbestos
(77536-68-6) and actinolite asbestos (77536-66-4).
2. Referenced Documents
The precise chemical composition of each species varies
4 with the location from which it was mined. Other amphibole
2.1 ASTM Standards:
minerals that exhibit the characteristics of asbestos have also
D257Test Methods for DC Resistance or Conductance of
been observed (6).
Insulating Materials
The nominal compositions of the most common asbestos
D1356Terminology Relating to Sampling and Analysis of
varieties are:
Atmospheres
Chrysotile Mg Si O (OH)
3 2 5 4
D1357Practice for Planning the Sampling of the Ambient
2+ 3+
Crocidolite Na Fe Fe Si O (OH)
2 3 2 8 22 2
Atmosphere
Amosite (Mg,Fe) Si O (OH)
7 8 22 2
Anthophyllite (Mg,Fe) Si O (OH)
D3670Guide for Determination of Precision and Bias of 7 8 22 2
2+
Tremolite Ca (Mg,Fe) Si O (OH) (Mg/(Mg + Fe ) 0.9 - 1.0)
2 5 8 22 2
Methods of Committee D22
2+
Actinolite Ca (Mg,Fe) Si O (OH) (Mg/(Mg + Fe ) 0.5 - 0.9)
2 5 8 22 2
D5337Practice for Flow RateAdjustment of Personal Sam-
3.1.3.1 Discussion—Actinolite compositions in which Mg/
pling Pumps
2+
(Mg+Fe ) is between 0 and 0.5 are referred to as ferroacti-
D6620Practice for Asbestos Detection Limit Based on
nolite.SeeRef. (7)forthefullnamingconventionsspecifiedby
Counts
the International Mineralogical Association.
D7200Practice for Sampling and CountingAirborne Fibers,
Including Asbestos Fibers, in Mines and Quarries, by 3.1.4 asbestos fiber, n—a fiber of asbestos, which meets the
Phase Contrast Microscopy and Transmission Electron criteria specified below for a fiber. Phase Contrast Microscopy
Microscopy (PCM) does not identify fibers as asbestos. Under the light
microscope, a population of asbestos fibers may appear as a
4 5
For referenced ASTM standards, visit the ASTM website, www.astm.org, or Available from United States Department of Health and Human Services
contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM (HHS), 200 Independence Ave., SW, Washington, DC 20201, http://www.hhs.gov.
Standards volume information, refer to the standard’s Document Summary page on Available from Asbestos International Association, 68 Gloucester Place,
the ASTM website. London, W1H 3HL, England.
D7201 − 06 (2020)
mixture of fiber agglomerates, fiber bundles (polyfilamentous area of 0.00785 mm ) with a cross-hair having tick-marks at
growth, unique to asbestiform fibers), fibers with split ends, 3-µm intervals in one direction and 5-µm intervals in the
andsinglefibers,therelativeoccurrenceandfrequencyofeach orthogonal direction. There are also examples around the
type depending on the situation. periphery of the circle to illustrate specific sizes and shapes of
fibers. This design of the graticule is shown in Fig. A1.1. The
3.1.5 aspect ratio, n—the ratio of the length of a fiber to its
graticule is placed in one of the microscope eyepieces so that
width.
the design is superimposed on the field of view.
3.1.6 differential counting, n—a term applied to the practice
of excluding certain kinds of fibers from the fiber count 4. Summary of Practice
because they do not appear to be morphologically consistent
4.1 Thesampleiscollectedbydrawingairthrougha25-mm
withfibersofaspecificvarietythusmodifyingthedefinitionof
diameter,mixedcelluloseester(MCE)membranefilter,housed
fiber given below.
in a conductive polypropylene cassette. After sampling, a
3.1.7 fiber, n—an elongated particle that is longer than 5.0
sector of the membrane filter is converted to an optically
µm, with a minimum aspect ratio of 3:1, and sometimes also
transparent homogeneous gel. Fibers longer than 5 µm are
classified as having a maximum width of 3.0 µm as this latter
counted by observing them with a PCM at a magnification
dimension may equate to the size of fiber, of the density of
between 400 and 500.
many silicate minerals, capable of penetrating to the lung. An
5. Significance and Use
asbestos fiber should further exhibit the asbestiform habit,
although analysis of airborne fibers by PCM may not be
5.1 Users of this practice must determine for themselves
sufficient to determine asbestiform habit. whether the practices described meet the requirements of local
or national authorities regulating asbestos or other fibrous
3.1.8 fibril, n—a single fiber of asbestos that cannot be
hazards.
further separated longitudinally into smaller components with-
out losing its fibrous properties or appearances.
5.2 Variations of this practice have been described by the
Asbestos Research Council in Great Britain (8), the Asbestos
3.1.9 fibrous, adj—ahabitofmineralscomposedofparallel,
International Association (AIA) RTM 1 (9), NIOSH 7400,
radiating, or interlaced aggregates of fibers, from which the
OSHAID160, and ISO 8672. Where the counting rules of the
fibers are sometimes separable.Acrystalline aggregate may be
latter three methods differ, this is noted in the text.
referred to as fibrous even if it is not composed of separable
fibers, but has that distinct appearance. The term “fibrous” in
5.3 Advantages:
mineralogy is used to describe aggregates of mineral grains
5.3.1 The technique is specific for fibers. PCM is a fiber
that crystallize in a needle-like habit and appear to be com-
countingtechniquethatexcludesnon-fibrousparticlesfromthe
posed of fibers. Asbestos minerals are fibrous, exhibiting a
analysis.
specifictypeoffibroushabittermedasbestiform.However,not
5.3.2 The technique is inexpensive, but requires specialized
all minerals having fibrous habit are asbestos.
knowledge to carry out the analysis for total fiber counts, at
3.1.10 field (of view), n—the area within a graticule circle least in so far as the analyst is often required under regulations
to have taken a specific training course (for example, NIOSH
that is superimposed on the microscope image.
582, or equivalent).
3.1.11 habit, n—the characteristic crystal growth form or
5.3.3 Theanalysisisquickandcanbeperformedon-sitefor
combination of these forms of a mineral, including character-
rapid determination of the concentrations of airborne fibers.
istic irregularities.
5.4 Limitations:
3.1.12 HSE/NPL test slide, n—a calibration slide designed
5.4.1 The main limitation of PCM is that fibers are not
to determine the limit of visibility of a PCM and an observer.
identified.Allfiberswithinthespecifieddimensionalrangeare
3.1.13 limit of detection, n—the number of fibers necessary
counted. Differential fiber counting may sometimes be used to
to be 95% confident that the result is greater than zero.
discriminate between asbestos fibers and fibers of obviously
3.1.14 personal sample, n—a sample taken by a collection
differentmorphology,suchascelluloseandglassfiber.Inmost
apparatus(membranefilter)positionedinthebreathingzoneof
situations, differential fiber counting cannot be used to ad-
the subject (near the nose and mouth) such that the collected
equately differentiate asbestos from non-asbestos fibers for
particles are representative of airborne dust that is likely to
purposes of compliance with regulations without additional
enter the respiratory system of the subject in the absence of
positive identification. If positive identification of asbestos is
respiratory protection.
required, this must be performed by polarized light or electron
microscopy techniques, using a different portion of the filter.
3.1.15 set, n—agroupofsamplesthatarecollected,submit-
ted to the laboratory, and analyzed for a report that is 5.4.2 A further limitation is that the smallest fibers visible
byPCMareabout0.2µmindiameter,whilethefinestasbestos
generated.
fibers may be as small as 0.02 µm in diameter.
3.1.16 Walton-Beckett graticule, n—an eyepiece graticule
5.4.3 Where calculation of fiber concentration provides a
specifically designed for asbestos fiber counting. It consists of
result exceeding the regulatory standard, non-compliance is
acirclewithanominalprojecteddiameterof100µm(nominal
assumed unless it can be proven that the fibers counted do not
belong to a member or members of the group of fibers
Health and Safety Executive/National Physical Laboratory – United Kingdom regulated by that standard.
D7201 − 06 (2020)
fields. Pre-counting of filters by the manufacturer may be accepted if
6. Interferences
confirmed by field blanks being within acceptable range.
6.1 If the practice is used to monitor a specific type of fiber,
NOTE 2—Cassettes shall not be re-used or re-loaded.
any other airborne fibers present will interfere because all
8.2 Sampling Pump—Forpersonalsampling,abatterypow-
particles meeting the counting criteria are counted. Some
ered pump, minimum flow rate 0.5 L/min (see 10.3 for
commonfibersthatmaycreateinterference,are:gypsum,plant
discussion on flow rate), with flexible connecting tubing. For
fibers, cellulose, perlite veins, diatoms, cellular plastic, mold
area sampling, a supply powered pump, capable of flow rates
mycelium, and cleavage fragments of minerals.
up to 16.0 L/min may be used in place of personal sampling
6.2 Particle aggregates consisting of chains of small
pumps when higher flow-rates or longer sampling times are
particles, such as smoke or welding fume, may be perceived to
desired.
be fibers and give rise to elevated results.
8.3 Microscope, positive phase (dark) contrast with a bin-
6.3 Platy particles such as talc sometimes can be oriented
ocular or trinocular head, green or blue filter, adjustable field
with the flat side perpendicular to the plane of the filter, and in
iris, wide-field or Huygenian 8× to10× eyepieces, and a 40× to
this orientation they may appear as countable fibers.
45× phase objective with numerical aperture 0.65 to 0.75, to
give a total magnification of approximately 400 to 450.
6.4 High levels of non-fibrous dust particles may obscure
fibers in the field of view and decrease the measured
NOTE 3—The eyepiece containing the graticule must be a focusing
concentration, seriously underestimating the actual exposure.
eyepiece.
NOTE 4—Köhler illumination should be used, if possible.
6.5 Some membrane filters have inhomogeneous regions in
8.4 Microscope Slides, Glass, pre-cleaned, 25 mm by 75
which the polymers are not properly mixed, and the clearing
mm. Slides with one end frosted are convenient for labeling
processgivesrisetofeaturesthatcannotbedistinguishedfrom
using a pencil, or alternatively, adhesive labels may be used.
fibers.
8.5 CoverSlips—22mmby22mm,No.1 ⁄2,unlessanother
6.6 Cleavage fragments of non-asbestiform anthophyllite,
thickness of cover slip is specified by the manufacturer of the
tremolite, actinolite and other minerals that have dimensions
objective lens.
within the range of the fiber definition in this practice will be
included in the fiber counting result.
8.6 Scalpel Holder and Disposable Blades—#10 or #22
surgical steel, curved blade.
7. Precautions
8.7 Forceps—Fine point.
7.1 Asbestos is a known carcinogen; as such proper venti-
8.8 Acetone Vaporizer—A device used to clear MCE filters
lation must be provided during the sample handling so as to
by exposure to a small amount of vaporized acetone.
minimizetheriskofinhalationbythetechnicianduringsample
preparation if the asbestos is suspected to be present in a form 8.9 Syringe, Hypodermic, with 22-gauge needle or dispos-
that may become airborne. Handle the samples in such a way able micropipet.
as to avoid causing the fibers to become an airborne inhalation
8.10 Graticule, Walton-Beckett (Type G22), with 100 µm
hazard.Tominimizetheriskofinhalationbytheanalystduring
diametercircularfieldattheplaneofthespecimen.Thedesign
sample preparation in the laboratory, the exterior of cassettes
of the graticule is shown in Fig. A1.1.
should be cleaned of visible dust and debris in the field before
NOTE 5—The graticule is custom-made for each microscope such that
they are submitted. Consult the materials safety data sheets for
the diameter of the circular field is 100 µm at the plane of the specimen.
asbestos and all reagents listed in Section 9.
It is necessary to specify the disc diameter needed to fit the ocular of the
microscope and the diameter (mm) of the circular counting area (see
8. Apparatus
Annex A1).
7 9
8.1 Sampler—25mmdiameter,three-piececonductive cas-
8.11 HSE/NPL phase contrast test slide—Mark II.
sette with 50-mm extension cowl and with a mixed cellulose
8.12 Telescope Ocular—Used for viewing and centering
ester filter, 0.45 to 1.2 µm pore size, supported by a back-up
phase-rings.
pad. Wrap the joint between the extension piece and cassette
8.13 Stage Micrometer—1 mm divided into 0.01 mm divi-
base with a shrink seal or tape to prevent dust from lodging in
sions.
thejoints.Ifothercassettesareused,theymustbeevaluatedto
ensure that the percentage of fiber losses to the walls does not
9. Reagents
exceedthoseofthestandardcassette,andthattheuniformityof
9.1 Acetone—reagent grade.
deposition across the filter is equivalent or better than that of
the standard cassette.
9.2 Triacetin (glycerol triacetate)—reagent grade.
NOTE 1—Analyze representative filters for fiber background before use
9.3 Lacquer or Nail Polish.
and reject the cassette lot if the average result is more than 5 fibers/100
The sole source of supply of the apparatus known to the committee at this time
“Conductive” as defined by ESD Association, 790 Turin Rd., Suite 4, Rome, is Optometrics USA, Nemco Way, Ayer MA, 01432 USA. If you are aware of
NY 13440, as having a resistance of less than 1×10 ohms per square surface. alternative suppliers, please provide this information to ASTM International
Conductance as measured by Test Methods D257. Conductivity should be assured Headquarters.Your comments will receive careful consideration at a meeting of the
by the manufacturer. responsible technical committee, which you may attend.
D7201 − 06 (2020)
10. Sampling Removeandreplacethecapsfromthefieldblankcassettesand
store the cassettes in a clean area (bag or box) during the
10.1 See Practice D1357 for guidance on sampling proce-
sampling period. Replace the caps in the cassettes when
dures.
sampling is completed. Average the field blank results and
10.2 Calibrate each sampling pump with a representative
subtract from the analytical results before reporting, if re-
cassette in line. Connect each pump to a calibration cassette
quired. Both NIOSH 7400 and OSHA ID160 require field
with an appropriate length of 6 mm [0.25 in.] bore plastic
blank results to be subtracted from the final result, but NIOSH
tubing.
7400 requires the reporting of field blank levels greater than 7
fibers/100 fields due to possible contamination. In other cases,
NOTE 6—This calibration cassette should be from the same lot of
cassettes used for sampling. blanks may not be required to be subtracted from the final
result. However, field blank results must always be reported
10.3 Select an appropriate flow rate for the situation being
and whether they have been subtracted from sample results.A
monitored. The sampling flow rate must be between 0.5 and
set consists of any sample or group of samples for which an
5.0 L/min for personal sampling and is commonly set between
evaluation for this practice must be made.
1 and 2 L/min. OSHA allows a maximum of 2.5 Lpm for
compliance sampling in General Industry (U.S. Code of
10.7 Sample at 0.5 L/min or greater (10). Where possible,
Federal Regulations: 29 CFR 1910.1001, Appendix A) and collect a minimum volume of 25 litres for personal samples
Construction Industry (29 CFR 1926.1101, Appendix A). The
(regulations governing area samples may prescribe greater
Maritime Industry (29 CFR 1915.1001, Appendix A) has a minimum volumes). For optimum counting precision, where
maximum of 5 Lpm. For area sampling, a flow rate of up to a
possible adjust the sampling flow rate, Q, and time, t,to
maximum of 16.0 L/min may be used. produce a fiber density, E, of 100 fibers/mm to 1300 fibers/
2 4 5
mm (3.85 × 10 to5×10 fibers on a 25 mm filter with an
NOTE 7—Do not overload the filter with dust. High levels of non-
effective collection area A of 385 mm ).
fibrous dust particles may obscure fibers on the filter and lower the count c
or make counting impossible. If more than about 25 to 30% of the field
A E
c
area is obscured with dust, the result may be biased low. Smaller air t 5 (1)
min
1000QL
volumes may be necessary when there is excessive non-asbestos dust in
theair(butaminimumof25Lshouldbetaken).Whilesampling,observe
where:
the filter with a small flashlight. If there is a visible layer of dust on the
t = minimum sampling time, minutes,
filter, stop sampling, remove and seal the cassette, and replace with a new min
A = effective collection area, mm ,
sampling assembly.
c
E = fiber density, fibers/mm ,
10.4 Calibrate sampling pumps before and after sampling
Q = sampling flow rate, L/min,
with a calibration cassette in-line, as close as possible to the
L = half the minimum concentration of interest to the
sampling site, using the procedures described in Practice
user of this practice, fibers/mL (or fibers/cm ), and
D5337. Note that a primary flow-rate calibrator can only be 3
1000 = conversion factor, mL (or cm)toL.
considered a primary standard for calibration purposes if the
NOTE 9—Periodically check and adjust the value of A due to
c
calibration is traceable to national standards (see Practice
variations, from manufacturer to manufacturer, of the effective collection
area of cassettes.
D5337).
10.8 Removethecassetteattheendofsampling,replacethe
NOTE 8—If calibration at the sampling site is not possible, environ-
plastic top cover and small end caps, and store the monitor.
mental influences may affect the flow rate.The extent is dependent on the
type of pump used. Consult the pump manufacturer to determine depen-
NOTE10—Donotreplacethecapandplugbeforeremovingthecassette
denceonenvironmentalinfluences.Ifthepumpisaffectedbytemperature
from an operating pump. This will cause a vacuum in the cassette and
and pressure changes, use the formula provided by the manufacturer to
rupture the filter, possibly displacing collected particulate from the filter
calculate the actual flow rate.
and destroying the value of any filter analysis.
10.5 Fasten the plastic tubing with spring clips or similar
10.9 If samples are shipped, it is recommended that the
devices on the worker’s lapel or other part of the worker’s
cassettes are packed in a rigid container. Pack the cassettes
clothing so that the cassette is as close as possible to the
tightly in static dissipative material such that they cannot be
worker’s mouth. Remove the plug from the outlet end of the
jostled or damaged in transit. Certain static-causing materials
cassette before starting the pump or attaching to an operating
are prohibited by regulation, including paper and non-
pump to avoid creating a vacuum inside the cassette and then
dissipative polystyrene packing materials (11, 12).
slowly remove the top cover from the end of the cowl
extension(openface)andorientthecassettefacedown.Ensure
11. Sample Preparation
that each cassette is held open side down in the worker’s
11.1 Wipe the exterior of the cassettes with a damp cloth
breathing zone during sampling.
before opening, to minimize the possibility of contaminating
10.6 The user must determine the blank level on the filters
the filter after opening the cassette.
to be used. As a guide to acceptability, the NIOSH 7400
11.2 Ensure that the glass slides and cover slips to be used
requires quality control on laboratory blank filters to be less
are free of dust and fibers.
than 5 fibers/100 fields (manufacturers test results are accept-
able). Each set of samples taken will include 10% field blanks
NOTE 11—The objective is to produce samples with a transparent,
or a minimum of two field blanks. These blanks must come
smooth (non-grainy) background in a medium with a refractive index
from the same lot as the filters used for sample collection. equaltoorlessthan1.46.Themethoddescribedbelowcollapsesthefilter
D7201 − 06 (2020)
for easier focusing and produces permanent mounts, which can be stored
to reduce the possibility of forming and trapping air bubbles
for quality control and inter laboratory comparisons. Alternative slide
between the cover slip and the filter. If too many bubbles form
preparation techniques may also be used (13).
or the amount of triacetin is insufficient, or too much time
11.3 Remove the top plug to prevent development of a
passes between the acetone and application of triacetin, the
vacuum when the cassette is opened. Using a scalpel or razor
cover slip may become detached within a few hours. Use only
blade, cut the seal, or tape around the cassette, or both, at the
enough triacetin to cover the filter. More will spill over the
depression between the base and the extension cowl. Very
edgeallowingforlaterfibermigration,minimizingthevalueof
carefullyseparatethebasefromtheextensioncowl,leavingthe
the slide preparation for archival purposes.
filter and back-up pad in the base. To avoid possible contami-
NOTE14—Allowingtheslidetostandforlongerthan30secondsbefore
nationofthefilter,donotusethesamescalpelthatwillbeused
the triacetin is added will result in an increased index of refraction of the
to cut the filter.
mountingmediumandconsequentlydecreasedcontrastbetweenthefibers
and the preparation.
11.4 Using forceps, grasp the filter at the perimeter of the
11.9 The clearing process is usually slow. The clearing
filter that was clamped between the cassette pieces. To do this
process may be accelerated by warming the slide on a hotplate
without damage to the filter, it is helpful to use a long, thin
(surface temperature 50 °C – 55 °C) or in an oven at this
object to push the back-up pad/filter pair above the base of the
temperature for 15 minutes.
cassette so the filter can be grasped from the edge. DO NOT
TOUCHthesurfaceofthefilter.Placethefilteronacleanglass 11.10 For samples retained for quality assurance or archival
slidewiththedepositsidefacingupwards.Afreshslideshould purposes, seal the edges of the cover slip to the glass slide
be used each time to eliminate possible cross-contamination. using a lacquer or nail polish (9). Samples with too much
An alternative approach that achieves the same aim is to cut a triacetin may be unsuitable for archival purposes, since the
wedge from the filter as it lies within the cassette. fibers may migrate.
11.5 Carefully examine the filter. Reject the filter if it does NOTE 15—It is recommended that the outline of the active collection
area of the filter sector be marked on the base of the slide, using a
notexhibitacompletecircularimpressionmadebytheedgeof
waterproof fiber-tipped pen, between the clearance and mounting steps.
the extension cowl, or if sharp edges on the extension cowl
This ensures that fiber counting is confined to the active collection area,
have cut through the filter. Observation of either situation is
andprovidesapermanentreferenceaftertheedgesofthefiltersectorhave
cause to reject the filter as defective, because leakage around
become difficult to see. Some movement of the particulate material will
continue to occur during storage, but this movement is not sufficient to
the edge of the filter in an improperly clamped cassette, or
significantly affect the reported results.
leakage through the cut areas of the filter, will lead to a
negative bias in the result.
12. Microscope Calibration
11.6 Cut90°sectorsofapproximately25%ofthefilterarea 12.1 Ensure that all optical surfaces are clean. Even a small
withacurvedbladesteelsurgicalscalpel(notthesameonethat
amount of dirt can significantly degrade the image.
was used to cut the perimeter band of the cassette). Place the
12.2 Microscope Adjustments—Follow the manufacturer’s
filter or sector, dust side up, on a clean, labeled, microscope
instructions and also the following:
slide. Static electricity will usually keep the filter on the slide
12.2.1 Adjust the light source for even illumination across
until it is cleared. Use care not to disturb the particles on the
the field of view at the condenser iris (see Note 4).
filter. Return the remainder of the filter to the cassette for
12.2.2 Focus the microscope on the particulate material to
storage.
be examined.
12.2.3 Ensure that the field iris is in focus, centered on the
NOTE 12—If preferred, the whole sample filter may be mounted and
cleared. However, this will not leave any sample filter available for sample and open only enough to fully illuminate the graticule
subsequent quality assurance measurements or optional examination by
field of view.
transmission electron microscopy.
12.2.4 Use the telescope ocular supplied by the manufac-
11.7 Inserttheslideintotheacetonevaporizer,centeringthe
turer to ensure that the phase rings (annular diaphragm and
filter sector under the delivery spout. Inject acetone in accor- phase-shifting elements) are accurately concentric. Critically
dance with the manufacturer’s instructions to clear the filter.
center the rings. Misalignment of the rings will result in
Remove the slide from the vaporizer. astigmatism and a degraded image.
12.3 Testing of the Visibility Performance of the Micro-
NOTE 13—Use a minimum volume of acetone. Excess acetone may
flush fibers from the filter yielding low results. For most acetone scope:
vaporizers, a nominal volume between 100-250 microlitres (µL) is
12.3.1 Periodically check the phase-shift detection limit of
appropriate for each slide. Acetone is extremely flammable and precau-
themicroscopeusingtheHSE/NPLphase-contrasttestslide,as
tions must be taken not to ignite it.Avoid using large containers or large
described in Annex A2.
quantities of acetone.Transfer the solvent in a ventilated laboratory hood.
12.3.2 If the image quality deteriorates, clean the micro-
Do not use acetone near any open flame. For generation of acetone vapor,
use a spark-free heat source.
scope optics, and if the problem persists, consult the micro-
scope manufacturer.
11.8 Immediately (less than 30 seconds), using the hypo-
dermic syringe with an approximately 22-gauge needle, or a 12.4 Ensure the size of the Walton-Beckett graticule (see
micro-pipette with a disposable tip, place 1 to 2 drops of Annex A1) is checked when received, and whenever the
triacetin on the filter surface. Gently lower a clean approxi- microscopeisdisassembled/reassembled,suchasduringmain-
mately 22 mm square cover slip onto the filter at a slight angle tenance or cleaning.
D7201 − 06 (2020)
13. Measurement 13.10 Count a bundle of fibers as one fiber unless the
individual constituent fibers can be clearly identified and each
13.1 FollowthealignmentroutinespecifiedinSection12at
individual constituent fiber is clearly not connected to another
the beginning of every counting session and more often if it is
counted fiber.
foundtobenecessary.Inparticular,checkthealignmentofthe
phase rings before counting each sample, because any slight 13.11 Record the number of fibers in each graticule field in
angle, which may sometimes exist between the slide and the a consistent way, using a data sheet such as that shown in Fig.
cover slip can result in misalignment of the phase rings. 1, so that any non-randomness in the filtered particulate can be
evaluated. If a field has no fibers counted, it must be recorded
13.2 Place the prepared sample slide on the mechanical
as “0” and not left blank.
stage of the microscope. Position the center of the filter sector
under the objective lens and focus upon the sample. 13.12 When an agglomerate (mass of material) or a bubble
coversmorethan25%ofthegraticulefield,rejectthegraticule
13.3 Start the count from one end of the filter sector and
field and select another. Do not include the rejected field in the
progress along a radial line to the other end.The count may be
number of graticule fields counted and always record such
performed in either direction from the perimeter to the tip of
occurrences. If the percentage of rejected fields exceeds 25%
thefiltersector.Selectfieldsrandomly,withoutlookingintothe
ofthetotalnumberoffields,thereisapossibilitythatthecount
eyepieces,byslightlyadvancingtheslideinonedirectionwith
may be biased low, and this situation should be reported. If the
the mechanical stage control.
number of rejected fields is too large to allow sufficient fibers
13.4 Selectgraticulefieldsatleast1mmfromthecutedges,
orfieldstobecountedinaccordancewith13.8,thenthesample
and at least 1 mm into the deposit area at the filter periphery.
should be rejected as overloaded.
Aline drawn on the slide around the inside of the periphery of
13.13 Follow the “A” counting rules described in Guide
the filter can aid in meeting this requirement.
D3670 for determination of suspected asbestos fibers.
13.5 Using the fine focus control, continually scan over a
13.14 Follow the “B” counting rules described in Practice
range of focal planes (generally the upper 10 to 15 µm of the
D5337 for determination of known non-asbestos fibers such as
filter surface) during the examination of each graticule field.A
glassandotherman-mademineralfibers.Iffibersareofmixed
minimumtimeof15secondsforexaminationofeachgraticule
or unknown composition use the “A” rules.
field is appropriate for accurate counting. Taking insufficient
timewillresultintheanalystmissingveryfinefibersiftheyare 13.15 Differential Fiber Counting—Phase Contrast Micros-
present. This is a common counting error when chrysotile copy does not provide positive confirmation of asbestos fibers.
fibers are present. This is a systematic bias (error). However, differential fiber counting may be based on morpho-
logical discrimination or polarized light analysis of fibers. A
13.6 All asbestos types exhibit fibers with diameters less
great deal of experience is required to routinely and correctly
than1µm.Examineeachgraticulefieldcarefullyforfaintfiber
perform differential fiber counting and OSHA ID160 states
images. Small diameter fibers will be very hard to see.
thatitshouldbe“discouragedunlesslegallynecessary.”Where
However, they are often an important contribution to the total
it has been performed it must be clearly noted. A fiber should
count.
be excluded from the count only if it is obviously not the fiber
13.7 Count only fibers longer than 5 µm that also have
species of interest. If there is a question whether a fiber is the
lengthtowidthratiosasdescribedinthechosencountingrules
species of interest, follow the rule: “when in doubt, count.”
“A”or“B”inAnnexA3andAnnexA4.Measurethelengthof
Practice D7200 provides further details on how fiber popula-
curved fibers along the curve.
tions may be classified into specific types, but the practice is
not covered in this practice.
13.8 Count all the fibers in at least 20 fields subject to
counting rules as in the tables in the appropriate AnnexA3 or
13.16 Modification of PCM Data by Transmission Electron
AnnexA4.Continuethecountuntileither100fibershavebeen
Microscopy (TEM)—When a fiber count by Phase Contrast
countedor100graticulefieldshavebeenexamined,whichever
Microscopy exceeds the limit value, and it is suspected that
occurs first. Count all of the fibers in the final graticule field.
there is interference by unregulated fiber species, the PCM
13.9 Any fiber lying entirely within the boundary of the fiber count may be modified by TEM measurement of the
proportion of the specific fibers in the PCM count. Follow the
Walton-Beckett graticule field shall be counted as 1.Any fiber
crossing the boundary of the Walton-Beckett graticule field procedure described in Appendix X1.
once, having one end within the circle, shall be counted as ⁄2.
14. Calculations of Fiber Concentration
If a fiber touches the circle of the graticule field, it is
considered to cross the line and shall be counted as ⁄2 . Do not 14.1 Calculate and report the fiber density on the filter, E,
count any fibers that are totally outside the graticule area. where:
D7201 − 06 (2020)
FIG. 1 Example of Suitable Laboratory Work Sheet for Recording of PCM Fiber Count
D7201 − 06 (2020)
F B membrane filter method. The following list describes some of
n n the common sources of error.
f b
E 5 (2)
A
f
15.2 Systematic Errors:
where:
15.2.1 Sampling:
E = fiber density, fibers/mm ,
15.2.1.1 Flow rate.
F = fiber count,
15.2.1.2 Sampling time.
B = mean field blank count,
15.2.1.3 Non-representative or biased sampling.
n = numberofgraticulefieldsexaminedduringcountingof
f
15.2.1.4 Contamination, accidental or deliberate.
the sample,
n = mean number of graticule fields examined during 15.2.2 Analytical:
b
counting of the field blanks, and
15.2.2.1 Effective filter area.
A = actualfieldarea(0.00785mm foraproperlycalibrated
f
15.2.2.2 Counting area.
Walton-Beckett graticule).
15.2.2.3 Filter mounting.
14.2 Calculate the concentration, C, of fibers in the air
15.2.2.4 Microscope adjustments.
volume sampled, V, using the effective collection area of the
15.2.2.5 Analyst biases and counting practices.
filter, A :
c
15.2.2.6 Cross contamination.
EA
c
C 5 (3)
15.3 Random Errors:
1000V
15.3.1 Sampling:
where:
15.3.1.1 Flow rate variability.
A = nominally, 385 mm for a 25-mm filter (this may
c
15.3.1.2 Random fluctuations of the airborne dust cloud.
vary from manufacturer to manufacturer and other
15.3.2 Analytical:
factors),
15.3.2.1 Fiber distribution on the filter.
C = concentration of fibers in the air volume sampled,
15.3.2.2 Non-randomdepositionofdustonthefilterleadsto
fibers/mL (or fibers/cm ),
gross errors, the magnitude of which cannot be estimated.
V = volume of air sampled, L, and
1000 = conversion factor, L to mL (or cm ).
Twenty or more fields must be counted to ensure that minor
divergence from randomness does not bias the result.
Amore conservative approach is to calculate the concentra-
15.3.2.3 Poisson errors.
tionwithoutblankcorrection,although,insuchcase,theblank
values shall still be reported along with whether or not the 15.3.2.4 As only small samples of the fibers deposited on
blank correction was applied. the filter are counted, errors arise in the estimation of the total
number of fibers on the entire filter face. Theoretically, the
14.3 Report the results as fibers/mL(or fibers/cm ). Use the
Poisson distribution defines the variation in fiber counts
number of significant figures appropriate for the accuracy of
resulting from viewing randomly selected counting fields on
the measurement. If multiple analyses are performed on a
the filter. If a minimum of 100 fibers is counted, and if a
sample, an average of the results shall be reported unless any
Poisson distribution were appropriate to the counting results,
of the results can be rejected for cause, for example, overload-
the relative standard deviation of the fiber counts would be
ing or quality issues as stated in Section 17. State in the report
10%. It has been shown experimentally that the actual
that the result is an average.
distribution of fiber counts can depart from that of Poisson, in
14.4 Also report the number of fields counted and the
which case the standard deviation may be greater.
number of fibers found. Report the area of the Walton-Beckett
15.4 Limitations of the Membrane Filter Method and Pre-
graticule and the area of the filter where these differ from the
sentation of Results:
nominal values given in 14.1 and 14.2.
15.4.1 Using typical parameters of 1 L/min flow rate for 8
14.5 Report as well, sampling parameter information such
hours, and a minimum filter loading of 5.5 fibers/100 graticule
as area or personal sample, air volume, field area, detection
areas, the theoretical limit of detection is 0.0045 fiber/mL (or
limit, upper and lower confidence limits, and counting rules
fiber/cm ). However, in many situations the level of back-
used. When the procedure has been carried out in compliance
grounddustlimitstheairvolumethatcanbecollected,andthe
with a specific method, the method should be reported.
practical limit of detection may therefore be much higher.
Differential coun
...