ASTM D6620-06

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
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Designation: D6620 – 06
Standard Practice for
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Asbestos Detection Limit Based on Counts
This standard is issued under the fixed designation D6620; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope 3. Terminology
1.1 This practice presents the procedure for determining the 3.1 Definitions of Terms Specific to This Standard:
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detection limit (DL) for measurements of fibers or structures 3.1.1 average, n—the sum of a set of measurements
using microscopy methods. (counts) divided by the number of measurements in the set.
1.2 This practice applies to samples of air that are analyzed 3.1.1.1 Discussion—The average is distinguished from the
either by phase contrast microscopy (PCM) or transmission mean. The average is calculated from data and serves as an
electron microscopy (TEM), and samples of dust that are estimate of the mean. The mean (also referred to as the
analyzed by TEM. population mean, expected value,or first moment) is a param-
1.3 The microscopy methods entail counting asbestos struc- eter of the underlying statistical distribution of counts.
tures and reporting the results as structures per cubic centime- 3.1.2 background, n—a statistical distribution of structures
ter of air (str/cc) or fibers per cubic centimeter of air (f/cc) for introduced by (i) analyst counting errors and (ii) contamination
airsamplesandstructurespersquarecentimeterofsurfacearea on an unused filter or contamination as a consequence of the
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(str/cm ) for dust samples. sample collection and sample preparation steps.
3.1.2.1 Discussion—This definition of background is spe-
2. Referenced Documents
cific to this practice. The only counting errors considered in
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2.1 ASTM Standards: this definition of background are errors that result in an
D1356 Terminology Relating to Sampling and Analysis of
over-count (that is, false positives).Analyst counting errors are
Atmospheres errors such as, determining the length of structures or fibers
D5755 Test Method for Microvacuum Sampling and Indi-
andwhether,basedonlength,theyshouldbecounted;counting
rect Analysis of Dust by Transmission Electron Micros- artifacts as fibers; determining the number of structures pro-
copy for Asbestos Structure Number Surface Loading
truding from a matrix; and interpreting a cluster as one, two, or
D6281 Test Method forAirborneAsbestos Concentration in
more structures that should be counted only as zero or one
AmbientandIndoorAtmospheresasDeterminedbyTrans- structure. For purposes of developing the DL, assume that
mission Electron Microscopy Direct Transfer (TEM)
background contamination sources have been reduced to their
D6480 Test Method for Wipe Sampling of Surfaces, Indi- lowest achievable levels.
rect Preparation, and Analysis for Asbestos Structure
3.1.3 blank, n—a filter that has not been used to collect
Number Surface Loading by Transmission Electron Mi- asbestos from the target environment.
croscopy
3.1.3.1 Discussion—Blanks are used in this practice to
E456 Terminology Relating to Quality and Statistics determinethedegreeofasbestoscontaminationthatisreflected
in asbestos measurements. Contamination may be on the virgin
filter or introduced in handling the filter in the field or when
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This practice is under the jurisdiction ofASTM Committee D22 onAir Quality
preparing it for inspection with a microscope. The data
and is the direct responsibility of Subcommittee D22.07 on Sampling and Analysis
required to determine the degree of contamination consists,
of Asbestos.
Current edition approved Oct. 1, 2006. Published October 2006. Originally
therefore, of measurements of field blanks that have experi-
approved in 2000. Last previous edition approved in 2000 as D6620 – 00. DOI:
enced the full preparation process.
10.1520/D6620-06.
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3.1.4 decision value, n—a numerical value used as a bound-
The DL also is referred to in the scientific literature as Limit of Detection
(LOD), Method Detection Limit (MDL), and other similar descriptive names. ary in a statistical test to decide between the null hypothesis
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For purposes of general exposition, the term “structures” will be used in place
and the alternative hypothesis.
of “fibers or structures.” In the examples in Section 8, the specific term, “fiber” or
3.1.4.1 Discussion—In the present context, the decision
“structure,” is used where appropriate.These terms are defined separately in Section
value is a structure count that defines the boundary between
3.
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For referenced ASTM standards, visit the ASTM website, www.astm.org, or
“below detection” (the null hypothesis) and “detection” (the
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