ASTM D6246-2008 374 Standard Practice for Evaluating the Performance of Diffusive Samplers《评价扩散采样器性能的标准实施规程》.pdf
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1、Designation: D 6246 08Standard Practice forEvaluating the Performance of Diffusive Samplers1This standard is issued under the fixed designation D 6246; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision. A nu
2、mber in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This practice covers the evaluation of the performanceof diffusive samplers of gases and vapors for use over samplingperiods from 4 to 1
3、2 h and for wind speeds less than 0.5 m/s.Such sampling periods and wind speeds are the most commonin the indoor workplace setting. This practice does not apply tostatic or area sampling in wind speeds less than 0.1 m/s, whendiffusion outside the sampler may dominate needed convectionfrom the ambien
4、t air to the vicinity of the sampler. Given asuitable exposure chamber, the practice can be extended tocover sampler use for other sampling periods and conditions.The aim is to provide a concise set of experiments forclassifying samplers primarily in accordance with a singlesampler accuracy figure.
5、Accuracy is defined (3.2.1) in thisstandard so as to take into account both imprecision anduncorrected bias. Accuracy estimates refer to conditions ofsampler use which are normally expected in a workplacesetting. These conditions may be characterized by the tempera-ture, atmospheric pressure, humidi
6、ty, and ambient wind speed,none of which may be constant or accurately known when thesampler is used in the field. Futhermore, the accuracy accountsfor the effects of diffusive loss of analyte on the estimation oftime-weighted averages of concentrations which may not beconstant in time. Aside from a
7、ccuracy, the samplers are testedfor compliance with the manufacturers stated limits on capac-ity, possibly in the presence of interfering compounds.1.2 This practice is an extension of previous research ondiffusive samplers (1-14)2as well as Practices D 4597, D 4598,D 4599, and MDHS 27. An essential
8、 advance here is theestimation of sampler accuracy under actual conditions of use.Futhermore, the costs of sampler evaluation are reduced.1.3 Knowledge gained from similar analytes expedites sam-pler evaluation. For example, interpolation of data character-izing the sampling of analytes at separated
9、 points of ahomologous series of compounds is recommended. At presentthe procedure of (9) is suggested. Following evaluation of asampler in use at a single homologous series member accord-ing to the present practice, higher molecular weight memberswould receive partial validations considering sampli
10、ng rate,capacity, analytical recovery, and interferences. The test fordiffusive analyte loss can be omitted if the effect is foundnegligible for a given sampler or analyte series.1.4 The values stated in SI units are to be regarded asstandard. No other units of measurement are included in thisstanda
11、rd.1.5 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. Reference
12、d Documents2.1 ASTM Standards:3D 1356 Terminology Relating to Sampling and Analysis ofAtmospheresD 4597 Practice for Sampling Workplace Atmospheres toCollect Gases or Vapors with Solid Sorbent DiffusiveSamplersD 4598 Practice for Sampling Workplace Atmospheres toCollect Gases or Vapors with Liquid S
13、orbent DiffusionalSamplers4D 4599 Practice for Measuring the Concentration of ToxicGases or Vapors Using Length-of-Stain Dosimeters2.2 International Standards:CEN EN 838 European Standard, Workplace atmospheres -Diffusive samplers for the determination of gases orvapours - Requirements and test meth
14、ods5MDHS 27 Protocol for assessing the performance of adiffusive sampler, Health and Safety Laboratory, UnitedKingdom6MDHS 80 Volatile organic compounds in air, Health andSafety Laboratory, United Kingdom63. Terminology3.1 Definitions:1This practice is under the jurisdiction of ASTM Committee D22 on
15、 Air Qualityand is the direct responsibility of Subcommittee D22.04 on Workplace Air Quality.Current edition approved April 1, 2008. Published May 2008. Originallyapproved in 1998. Last previous edition approved in 2002 as D 6246 - 02.2The boldface numbers in parentheses refer to the list of referen
16、ces 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.4Withdrawn5Available from CEN
17、Central Secretariat, rue de Stassart 36, B-1050 Brussels,Belgium.6Available from HMSO Books, PO Box 276, London, England, SW8 5DT.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.3.1.1 For definitions of terms used in this practice, r
18、efer toTerminology D 1356.3.2 Definitions of Terms Specific to This Standard:3.2.1 Symmetric Accuracy Range Athe fractional range,symmetric about the true concentration c, within which 95 %of sampler measurements are to be found (14-19). In terms ofthe bias D relative to true concentrations and the
19、total (true)relative standard deviation RSD (sometimes designated asTRSD), the accuracy range A is closely approximated (19) by:A 5H1.960 3 =D21 RSD2, if |D| , RSD / 1.645|D| 1 1.645 3 RSD, otherwise(1)3.2.1.1 DiscussionIn the case that bias is corrected, leav-ing only an uncorrectable residual bias
20、 due to uncertainty in thecorrection, 95 %-confidence limits on A play the role of theexpanded uncertainty in (20). As described in (14), such aninterpretation is an extension of (20) for measurement, as inoccupational hygiene, of concentrations which are neitherspatially nor temporally constant. Ra
21、ther than continuallyre-evaluating a method through estimate replicates, the accu-racy provides confidence intervals bracketing (true) concentra-tions at greater than a given probability (95 %) for a fixedconfidence (95 %) in the initial sampler evaluation. Suchintervals with double confidence level
22、s (in both measurementand evaluation) are related to a branch of statistics known asthe theory of tolerance or prediction intervals.3.2.2 diffusive samplera device which is capable of takingsamples of gases or vapors from the atmosphere at a ratecontrolled by a physical process such as gaseous diffu
23、sionthrough a static air layer or permeation through a membrane,but which does not involve the active movement of air throughthe sampler. As such, direct-reading dosimeters, as well assamplers requiring lab analysis, are considered diffusive sam-plers within this practice.3.3 Symbols:A = symmetric a
24、ccuracy range as defined in termsof bias and imprecision = estimated symmetric accuracy range AA95 %= 95 % confidence limit on the symmetric ac-curacy range Ac (mg/m3) = true or reference analyte concentrationc (mg/m3) = mean of (four) concentration estimates (in-cluding (p, T)-corrections) obtained
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