1、Designation: D4597 10Standard Practice forSampling Workplace Atmospheres to Collect Gases orVapors with Solid Sorbent Diffusive Samplers1This standard is issued under the fixed designation D4597; the number immediately following the designation indicates the year oforiginal adoption or, in the case
2、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.1. Scope1.1 This practice covers the sampling of workplace atmo-spheres for the presence of certain gases
3、 or vapors by means ofdiffusion across a specified quiescent region and subsequentsorption on a solid sorbent (1).21.2 A list of organic compounds which are applicable tosolid sorbent sampling where the sorbent is contained in a bedthrough which air is passed is given in Annex A1 of PracticeD3686. D
4、iffusive samplers may be applicable to a similarrange of compounds but this must be confirmed by reference tothe individual sampler manufacturers literature.1.3 The valid use of diffusive samplers depends on theexistence of actual laboratory or field validation, or both.Guidance on validation can be
5、 obtained from published proto-cols (2-6). This practice is not designed to cover the verifica-tion, validation, or specific test procedures used to assess theaccuracy or precision of diffusive samplers.1.4 The values stated in SI units shall be regarded as thestandard.1.5 This standard does not pur
6、port 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:3D1
7、356 Terminology Relating to Sampling and Analysis ofAtmospheresD3686 Practice for Sampling Atmospheres to Collect Or-ganic Compound Vapors (Activated Charcoal Tube Ad-sorption Method)D3687 Practice for Analysis of Organic Compound VaporsCollected by the Activated Charcoal Tube AdsorptionMethodD6306
8、Guide for Placement and Use of Diffusion Con-trolled Passive Monitors for Gaseous Pollutants in IndoorAir2.2 Other Document:4Title 29CFR 1910.1000 Subpart Z Occupational Health andSafety Standard3. Terminology3.1 Terminology D1356 contains definitions of terms usedin this practice.3.2 Definitions of
9、 Terms Specific to This Standard:3.2.1 diffusionthe movement of gas or vapor moleculesfrom a region of high concentration to a region of lowconcentration as described by Ficks first law (8.1).3.2.2 diffusive samplerassembly used for sampling gas orvapor molecules from the atmosphere.3.2.3 sampling r
10、atethe ratio of mass of a given compoundcollected by a diffusive sampler per unit time of exposure to theconcentration of that compound in the atmosphere beingsampled. The sampling rate is sometimes referred to as theuptake rate. Units are ng (or mg)/ mg/m3/min (or h), which aredimensionally equival
11、ent to a volume flow-rate (for examplecm3/min).4. Summary of Practice4.1 Molecules (gases and vapors) are sampled from theatmosphere by a diffusive sampler. During the samplingprocess, the molecules diffuse from the environment adjacentto the sampler through a region of defined geometric structurean
12、d into a region containing the sorbent medium. The theory ofdiffusive sampling is given in this practice.4.2 Instructions are given for the correct use of the samplingdevices to enable their field application.4.3 Information on the calculation of environmental concen-tration based on sampler assay i
13、s given.1This practice is under the jurisdiction of ASTM Committee D22 on Air Qualityand is the direct responsibility of Subcommittee D22.04 on Workplace Air Quality.Current edition approved Nov. 1, 2010. Published January 2011. Originallyapproved in 1987. Last previous edition approved in 2010 as D
14、4597 03(2009)1.DOI: 10.1520/D4597-10.2The boldface numbers in parentheses refer to the list of references at the end ofthis practice.3For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume infor
15、mation, refer to the standards Document Summary page onthe ASTM website.4Code of Federal Regulations, available from U.S. Government Printing Office,Washington, DC 20402.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.5. Significance
16、 and Use5.1 Regulations such as those promulgated by the U.S.Occupational Safety and Health Administration in 29 CFR1910.1000 designate that certain hazardous gases and vaporsmust not be present in the workplace air at concentrationsabove specific values.5.2 This practice, when used in conjunction w
17、ith an analyti-cal technique, such as that given for organic compounds inPractice D3687, may provide a means for the determination oftime-weighted airborne concentrations of many of the hazard-ous gases and vapors in applicable regulations (for example,29CFR 1919.1000,), as well as others.5.3 The ma
18、nufacturers literature should be consulted forthe appropriate list of chemicals which may be sampled by aparticular device.6. Interferences6.1 The diffusive sampling process can be jeopardized byphysical blockage of entrances to the interior of the device suchas by liquid droplets or dust particles.
19、6.2 The diffusive sampling process can be jeopardized bystructural damage to any membranes or other elements used tocontrol either the geometry of the diffusion path or turbulencewithin the diffusion path.6.3 The diffusive sampling process can be jeopardized byair movement within the diffusion path.
20、 Recent sampler de-signs have incorporated elements to decrease this possibility.6.4 The diffusive sampling process can be jeopardized byinsufficient mixing of the air external to the sampler. This isknown as starvation. The manufacturer should provide arecommended minimum ambient air velocity, belo
21、w which thesampler should not be used.6.5 The diffusive sampling process can be jeopardized if theconcentration in air at the sorbent interface becomes sufficientto significantly alter the diffusion gradient within the diffusionpath. This can occur through sorbent saturation, either from thepresence
22、 of competing species (which may include water vapormolecules), or the selection of an inappropriate sorbent mate-rial for the concentration and time of exposure, or by increasedtemperature. The manufacturer should provide, or the usershould determine, the range of conditions over which signifi-cant
23、 bias from sorbent saturation will not occur.6.6 Errors may arise in estimating exposure using diffusivesamplers in instances in which the concentration of the gas orvapor being sampled varies significantly over time.6.7 Where multiple gases or vapors are sampled simulta-neously, care must be exerci
24、sed to ensure there is no mutualinterference in the analytical method chosen.7. Apparatus7.1 Diffusive Sampling Devices:7.1.1 A diffusive sampler consists of a cavity or group ofcavities containing air and terminated at one end by a sorbentsubstrate and opening at the other to the environment. Theca
25、vity or group of cavities form a region of defined geometrywhich acts as a control on the rate of gaseous diffusion from theexternal environment to the sorbent substrate. Barriers to theentry of external air movements are common. Samplers wherethe diffusion of gas or vapor is through materials other
26、 than airare covered by this practice, but it should be noted that theinfluence of temperature on diffusion may be more pro-nounced.7.1.2 Diffusive samplers are equipped with a means ofattachment to the body for personal sampling or to a suitablesupport for area sampling. Samplers are contained in v
27、aporimpermeable packages or are sealed with vapor impermeablecaps both before and after sampling. Labels for unique identi-fication of a collected sample are required.8. Diffusive Sampling Theory8.1 Ficks first law of diffusion states that for a constantconcentration gradient, the mass of material t
28、ransferred to thesampling layer can be expressed as follows:M 5DALC 2 Co!t (1)where:M = mass of material, ng,D = diffusion co-efficient, cm2/min (Note 1),A = cross sectional area of diffusion cavity(ies), cm2(Note2),L = length of diffusion path, cm (Note 3),C = gas phase concentration at face of sam
29、pler, ng/cm3,Co= gas phase concentration at sorbent surface, ng/cm3,andt = exposure time, min.NOTE 1The diffusion coefficient of a molecule is a function of thetemperature and the nature of the medium through which it is diffusing.Should the medium be a compressible fluid (for example, air) the diff
30、usioncoefficient will also be a function of the pressure.NOTE 2The presence of barriers to the entry of external air move-ments may alter the effective cross-sectional area of the sampler.NOTE 3Under certain circumstances the length of the diffusion pathcan be significantly extended into the thickne
31、ss of the sorbent layer duringsampling. Certain types of sampler make use of this phenomenon to givea length of stain read-out. In this situation, the mathematical treatment ofFicks law is more complex than that given here.8.2 The sampling rate (SR) of a diffusive sampler for aspecific gas or vapor
32、may be expressed as follows:SR 5DAL5MC 2 Co!t(2)where:SR = sampling rate, cm3/min.where:concentration (C, Co) is given in ppm (v/v) the units of SRbecome ng/ppm/min.8.2.1 Sampling rates may be estimated from diffusion coef-ficient ratios if the sampling rate of one substance is known:SR25 D2SR1D1(3)
33、However, where diffusion coefficients are calculated valuesrather than measurements, the potential for error exists in thisprocedure. Where possible, sampling rates should be confirmedby the results of experimental protocols.8.2.2 The sampling rate for a gas or vapor through air istheoretically prop
34、ortional to T1.5/P where T is the absoluteD4597 102temperature (in K) and P is the pressure (in kPa) (7); while inpractice, the concomitant air volume changes result in apparentsampling rate changes of 0.2 % per K and virtually nopressure effects. However, the exposure limits given in 29CFR1910.1000
35、 Subpart Z are referenced to standard temperatureand pressure (STP). Therefore, in order to compare a concen-tration value (in ppm) from a diffusive sampler with a federalexposure limit, it is necessary to convert the value to STP(11.6) (8).8.2.3 Sampling rates for gases or vapors using samplerswhic
36、h use a medium other than air in the diffusion path requiredifferent correction factors than given here. The manufacturersliterature should be consulted.8.3 Some samplers are available with the ability to samplemultiple gases or vapors simultaneously. Manufacturers litera-ture should be consulted.8.
37、4 Some samplers are equipped with a means of determin-ing the point of sorbent saturation. Refer to specific manufac-turers literature for information.9. Sampling with Diffusive Samplers9.1 Calibration of the Diffusive SamplerThe samplingrate of a diffusive sampler is determined by the diffusioncoef
38、ficient of the gas or vapor being sampled and the geometryof the diffusion path. It is normally provided by the manufac-turer. This theoretical sampling rate can be checked by experi-ment according to published protocols. These protocols includetests under all the conditions and combinations of cond
39、itionsthat might apply in a normal workplace setting, and the resultscan be analyzed to discern the conditions or combination ofconditions that might significantly influence the sampling rate.The results of these experiments are normally available fromthe manufacturer and they should be consulted by
40、 the user todetermine whether a particular sampler is appropriate for use ina specific workplace.9.2 Field Sampling with Diffusive Samplers:9.2.1 Follow the manufacturers instructions for use. Ingeneral, the following steps are involved:9.2.1.1 Open the sampler container at the time sampling isto be
41、 initiated.9.2.1.2 Initiate the sampling in accordance with the manu-facturers instructions. Identify the sampler and all containersto be used as required.9.2.1.3 Record the start time.9.2.1.4 Record all pertinent information such as tempera-ture, barometric pressure, relative humidity, ambient air
42、veloc-ity (for area samples), and gases and vapors being sampled.9.2.1.5 At the end of the sampling period, remove thesampler, follow the manufacturers instructions for handlingand sealing the sampler, and record the end time. Submit thesamples to a laboratory for analysis or perform any on-siteread
43、-out or analysis that may be possible.9.2.1.6 For a breathing zone sample, attach the sampler tothe workers clothing as near the breathing zone as possible.Ensure the open face of the sampler is facing toward theenvironment and exposed for the entire sampling period.9.2.1.7 For an area sample, posit
44、ion the sampler at thedesired point. Ensure that the ambient air velocity at thesampler position is above the minimum velocity recommendedby the manufacturer.9.3 Sampling Time:9.3.1 The minimum sampling time is governed by thesampling rate and by the sensitivity of the analytical method.Consult the
45、manufacturers instructions for the appropriateminimum recommended sampling time.9.3.2 The maximum sampling time is governed by thesampling rate and by the capacity of the sampler. Consult themanufacturers instructions for the maximum recommendedsampling time.9.3.2.1 When the maximum recommended samp
46、ling time isless than the desired sampling period, use two or moresamplers in sequence to accommodate the desired exposureperiod.9.4 Sampler Blanks:9.4.1 Present at least two samplers for analysis as fieldblanks with every set of ten samplers up to a maximum of tenblanks. The purpose of the field bl
47、ank is to detect the presenceof gases or vapors other than those in the sampled atmosphere.9.4.1.1 To prepare a field blank, remove an unexposedsampler from its package and then reseal it immediately.9.4.1.2 Do not use results from field blanks to correctsample results. If a field blank shows contam
48、ination, thesamples taken must be assumed to be contaminated andappropriate action taken.9.4.2 Media blanks are unopened samplers that are alsosubmitted for analysis. These need not be taken into the field.The results are used to correct sample results. Include at leastone media blank per analytical
49、 batch. Consult the manufactur-ers instructions for the appropriate number.10. Handling and Shipping of Samples10.1 Where samples are shipped to a laboratory for subse-quent analysis, take precautions to minimize sample losses andprevent extraneous contamination.10.1.1 Seal samples securely and identify (label) clearly.10.1.2 Follow manufacturers instructions concerning maxi-mum temperature of shipping and storage. This may varydepending on the sampled analyte.10.1.3 Samples shipped in aircraft cargo holds may besubject to contamination (for example, jet
