ASTM_D_7440_-_08_2015e1.pdf

Designation:D744008(Reapproved 2015)1Standard Practice forCharacterizing Uncertainty in Air Quality Measurements1This standard is issued under the fixed designation D7440;the number immediately following the designation indicates the year oforiginal adoption or,in the case of revision,the year of last revision.A number in parentheses indicates the year of last reapproval.Asuperscript epsilon()indicates an editorial change since the last revision or reapproval.1NOTEEditorial corrections were made throughout in July 2015.1.Scope1.1 This practice is for assisting developers and users of airquality methods for sampling concentrations of both airborneand settled materials in characterizing measurements as touncertainty.Where possible,analysis into uncertainty compo-nents as recommended in the ISO Guide to the Expression ofUncertainty in Measurement(ISO GUM,(1)2)is suggested.Aspects of uncertainty estimation particular to air qualitymeasurement are emphasized.For example,air quality assess-ment is often complicated by:the difficulty of taking replicatemeasurements owing to the large spatio-temporal variation inconcentration values to be measured;systematic error or bias,both corrected and uncorrected;and the(rare)non-normaldistribution of errors.This practice operates mainly throughexample.Background and mathematical development are rel-egated to appendices for optional reading.1.2 This standard 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 Standards:3D1356 Terminology Relating to Sampling and Analysis ofAtmospheresD3670 Guide for Determination of Precision and Bias ofMethods of Committee D22D6246 Practice for Evaluating the Performance of DiffusiveSamplersD6552 Practice for Controlling and Characterizing Errors inWeighing Collected Aerosols2.2 Other International Standards:ISO GUM Guide to the Expression of Uncertainty inMeasurement,ISO Guide 98,1995(See Ref(1),for anadditional measurement uncertainty resource.)4ISO 7708 Air QualityParticle Size Fraction Definitions forHealth-Related Sampling4ISO 15767 Workplace AtmospheresControlling and Char-acterizing Errors in Weighing Collected Aerosol4ISO 16107 Workplace AtmospheresProtocol for Evaluat-ing the Performance of Diffusive Samplers,20074EN 482 Workplace AtmospheresGeneral Requirementsfor the Performance of Procedures for the Measurement ofChemical Agents43.Terminology3.1 DefinitionsFor definitions of terms used in thispractice,see Terminology D1356.3.2 Other terms defined as follows are taken from ISO GUMunless otherwise noted:3.2.1 accuracycloseness of agreement between the resultof a measurement and a true value of the measurand.3.2.2 combined standard uncertainty,ucstandard uncer-tainty of the result of a measurement when that result isobtained from the values of a number of other quantities,equalto the positive square root of a sum of terms,the terms beingthe variances or covariances of these other quantities weightedaccording to how the measurement result varies with changesin these quantities.3.2.2.1 DiscussionAs within ISO GUM,the“other quan-tities”are designated uncertainty components ujfrom source j.The component ujis taken as the standard deviation estimatefrom source j in the case of a source of random variation.3.2.3 coverage factor,knumerical factor used as a multi-plier of the combined standard uncertainty(uc)in order toobtain an expanded uncertainty(U).1This practice is under the jurisdiction ofASTM Committee D22 on Air Qualityand is the direct responsibility of Subcommittee D22.01 on Quality Control.Current edition approved July 1,2015.Published July 2015.Originally approvedin 2008.Last previous edition approved in 2008 as D7440 08.DOI:10.1520/D7440-08R15E01.2The boldface numbers in parentheses refer to the list of references at the end ofthis standard.3For 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.4BIPM version available for download from http:/www.bipm.org/en/publications/guides/gum.html.ISO version available from American NationalStandards Institute(ANSI),25 W.43rd St.,4th Floor,New York,NY 10036,http:/www.ansi.org.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 3.2.3.1 DiscussionThe factor k depends on the specificmeaning attributed to the expanded uncertainty U.However,for simplicity this practice adopts the now nearly traditionalcoverage factor as the value 2,determining the specificmeaning of the expanded uncertainty U in different circum-stances.Other coverage factors if needed are then easilyimplemented simply by multiplication of the traditional e