1、Designation:D662006(Reapproved 2010)Standard Practice forAsbestos Detection Limit Based on Counts1This standard is issued under the fixed designation D6620;the number immediately following the designation indicates the year oforiginal adoption or,in the case of revision,the year of last revision.A n
2、umber in parentheses indicates the year of last reapproval.Asuperscript epsilon()indicates an editorial change since the last revision or reapproval.1.Scope1.1 This practice presents the procedure for determining thedetection limit(DL)2for measurements of fibers or structures3using microscopy method
3、s.1.2 This practice applies to samples of air that are analyzedeither by phase contrast microscopy(PCM)or transmissionelectron microscopy(TEM),and samples of dust that areanalyzed by TEM.1.3 The microscopy methods entail counting asbestos struc-tures and reporting the results as structures per cubic
4、 centime-ter of air(str/cc)or fibers per cubic centimeter of air(f/cc)forair samples and structures per square centimeter of surface area(str/cm2)for dust samples.1.4 The values stated in SI units are to be regarded asstandard.No other units of measurement are included in thisstandard.1.5 This stand
5、ard does not purport to address all of thesafety concerns,if any,associated with its use.It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2.Referenced Documents2.1 ASTM S
6、tandards:4D1356 Terminology Relating to Sampling and Analysis ofAtmospheresD5755 Test Method for Microvacuum Sampling and IndirectAnalysis of Dust by Transmission Electron Microscopyfor Asbestos Structure Number Surface LoadingD6281 Test Method for Airborne Asbestos Concentration inAmbient and Indoo
7、r Atmospheres as Determined byTransmission Electron Microscopy Direct Transfer(TEM)D6480 Test Method for Wipe Sampling of Surfaces,IndirectPreparation,and Analysis for Asbestos Structure NumberSurface Loading by Transmission Electron MicroscopyE456 Terminology Relating to Quality and Statistics3.Ter
8、minology3.1 Definitions of Terms Specific to This Standard:3.1.1 average,nthe sum of a set of measurements(counts)divided by the number of measurements in the set.3.1.1.1 DiscussionThe average is distinguished from themean.The average is calculated from data and serves as anestimate of the mean.The
9、mean(also referred to as thepopulation mean,expected value,or first moment)is a param-eter of the underlying statistical distribution of counts.3.1.2 background,na statistical distribution of structuresintroduced by(i)analyst counting errors and(ii)contaminationon an unused filter or contamination a
10、s a consequence of thesample collection and sample preparation steps.3.1.2.1 DiscussionThis definition of background is spe-cific to this practice.The only counting errors considered inthis definition of background are errors that result in anover-count(that is,false positives).Analyst counting erro
11、rs areerrors such as,determining the length of structures or fibersand whether,based on length,they should be counted;countingartifacts as fibers;determining the number of structures pro-truding from a matrix;and interpreting a cluster as one,two,ormore structures that should be counted only as zero
12、 or onestructure.For purposes of developing the DL,assume thatbackground contamination sources have been reduced to theirlowest achievable levels.3.1.3 blank,na filter that has not been used to collectasbestos from the target environment.3.1.3.1 DiscussionBlanks are used in this practice todetermine
13、 the degree of asbestos contamination that is reflectedin asbestos measurements.Contamination may be on the virginfilter or introduced in handling the filter in the field or whenpreparing it for inspection with a microscope.The datarequired to determine the degree of contamination consists,therefore
14、,of measurements of field blanks that have experi-enced the full preparation process.1This practice is under the jurisdiction ofASTM Committee D22 on Air Qualityand is the direct responsibility of Subcommittee D22.07 on Sampling and Analysisof Asbestos.Current edition approved Oct.1,2010.Published N
15、ovember 2010.Originallyapproved in 2000.Last previous edition approved 2006 as D6620 06.DOI:10.1520/D6620-06R10.2The DL also is referred to in the scientific literature as Limit of Detection(LOD),Method Detection Limit(MDL),and other similar descriptive names.3For purposes of general exposition,the
16、term“structures”will be used in placeof“fibers or structures.”In the examples in Section 8,the specific term,“fiber”or“structure,”is used where appropriate.These terms are defined separately in Section3.4For referenced ASTM standards,visit the ASTM website,www.astm.org,orcontact ASTM Customer Service at serviceastm.org.For Annual Book of ASTMStandards volume information,refer to the standards Document Summary page onthe ASTM website.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,