1、Designation: D 4597 03Standard Practice forSampling Workplace Atmospheres to Collect Gases orVapors with Solid Sorbent Diffusive Samplers1This standard is issued under the fixed designation D 4597; the number immediately following the designation indicates the year oforiginal adoption or, in the cas
2、e of revision, the year of last revision. A number 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 sampling of workplace atmo-spheres for the presence of certain ga
3、ses 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 PracticeD 368
4、6. Diffusive 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 ca
5、n be 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 This standard does not purport to address all of thesafety concerns, if any, associated w
6、ith 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:3D 1356 Terminology Relating to Sampling and Analysis ofAtmosphere
7、sD 3686 Practice for Sampling Atmospheres to Collect Or-ganic Compound Vapors (Activated Charcoal Tube Ad-sorption Method)D 3687 Practice for Analysis of Organic Compound VaporsCollected by the Activated Charcoal Tube AdsorptionMethodD 6306 Guide for Placement and Use of Diffusion Con-trolled Passiv
8、e Monitors for Gaseous Pollutants in IndoorAir2.2 Other Document:4Title 29CFR 1910.1000 Subpart Z Occupational Health andSafety Standard3. Terminology3.1 Terminology D 1356 contains definitions of terms usedin this practice.3.2 Definitions of Terms Specific to This Standard:3.2.1 diffusionthe moveme
9、nt 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 ratethe ratio of mass of a given compoundcollected by a dif
10、fusive 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 equivalent to a volume flow-rate (for examplecm3/min).4. Summary
11、of Practice4.1 Molecules are sampled from the atmosphere by adiffusive sampler. During the sampling process, the moleculesdiffuse from the environment adjacent to the sampler througha region of defined geometric structure and into a regioncontaining the sorbent medium. The theory of diffusive sam-pl
12、ing is given in this practice.1This practice is under the jurisdiction of ASTM Committee D22 on Air Qualityand is the direct responsibility of Subcommittee D22.04 on Workplace Atmo-spheres.Current edition approved April 10, 2003. Published June 2003. Originallyapproved in 1987. Last previous edition
13、 approved in 1997 as D 4597 97.2The 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 information
14、, 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.4.2 Instructions are
15、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 is given.5. Significance and Use5.1 Promulgations by the Federal Occupational Safety andHealth Administration in 29 CFR 1910.10
16、00 designate thatcertain hazardous gases and vapors must not be present in theworkplace air at concentrations above specific values.5.2 This practice, when used in conjunction with an analyti-cal technique, such as that given for organic compounds inPractice D 3687, may provide a means for the deter
17、mination oftime-weighted airborne concentrations of many of the hazard-ous gases and vapors in 29CFR 1919.1000, as well as others.5.3 The manufacturers literature should be consulted forthe appropriate list of chemicals which may be sampled by aparticular device.6. Interferences6.1 The diffusive sam
18、pling process can be jeopardized byphysical blockage of entrances to the interior of the device suchas by liquid droplets or dust particles.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
19、 path or turbulencewithin the diffusion path.6.3 The diffusive sampling process can be jeopardized byair movement within the diffusion path. Recent sampler de-signs have incorporated elements to decrease this possibility.6.4 The diffusive sampling process can be jeopardized byinsufficient mixing of
20、the air external to the sampler. This isknown as starvation. The manufacturer should provide arecommended minimum ambient air velocity, below which thesampler should not be used.6.5 The diffusive sampling process can be jeopardized if theconcentration in air at the sorbent interface becomes sufficie
21、ntto significantly alter the diffusion gradient within the diffusionpath. This can occur through sorbent saturation, either from thepresence of competing species (which may include water vapormolecules), or the selection of an inappropriate sorbent mate-rial for the concentration and time of exposur
22、e, or by increasedtemperature. The manufacturer should provide, or the usershould determine, the range of conditions over which signifi-cant 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
23、gas orvapor being sampled varies significantly over time.6.7 Where multiple gases or vapors are sampled simulta-neously, care must be exercised 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
24、cavity or group ofcavities containing air and terminated at one end by a sorbentsubstrate and opening at the other to the environment. Thecavity 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
25、substrate. Barriers to theentry of external air movements are common. Samplers wherethe diffusion of gas or vapor is through materials other 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
26、 equipped with a means ofattachment to the body for personal sampling or to a suitablesupport for area sampling. Samplers are contained in vaporimpermeable packages or are sealed with vapor impermeablecaps both before and after sampling. Labels for unique identi-fication of a collected sample are re
27、quired.8. Diffusive Sampling Theory8.1 Ficks first law of diffusion states that for a constantconcentration gradient, the mass of material transferred 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 = cr
28、oss sectional area of diffusion cavity(ies), cm2(Note2),L = length of diffusion path, cm (Note 3),C = gas phase concentration at face of sampler, 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 the
29、temperature and the nature of the medium through which it is diffusing.Should the medium be a compressible fluid (for example, air) the diffusioncoefficient 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-se
30、ctional area of the sampler.NOTE 3Under certain circumstances the length of the diffusion pathcan be significantly extended into the thickness 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 mathemati
31、cal 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 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
32、/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)However, where diffusion coefficients are calculated valuesrather than measurements, the potential for error exists in thisD4597032procedure. Where possible, sa
33、mpling rates should be confirmedby the results of experimental protocols.8.2.2 The sampling rate for a gas or vapor through air istheoretically proportional to T1.5/P where T is the absolutetemperature (in K) and P is the pressure (in kPa) (7); while inpractice, the concomitant air volume changes re
34、sult in apparentsampling rate changes of 0.2 % per K and virtually nopressure effects. However, the exposure limits given in 29CFR1910.1000 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
35、 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 samplerswhich use a medium other than air in the diffusion path requiredifferent correction factors than given here. The manufacturersliterature should be consulted.8.3 Some
36、 samplers are available with the ability to samplemultiple gases or vapors simultaneously. Manufacturers litera-ture should be consulted.8.4 Some samplers are equipped with a means of determin-ing the point of sorbent saturation. Refer to specific manufac-turers literature for information.9. Samplin
37、g with Diffusive Samplers9.1 Calibration of the Diffusive SamplerThe samplingrate of a diffusive sampler is determined by the diffusioncoefficient 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
38、 be checked by experi-ment according to published protocols. These protocols includetests under all the conditions and combinations of conditionsthat might apply in a normal workplace setting, and the resultscan be analyzed to discern the conditions or combination ofconditions that might significant
39、ly influence the sampling rate.The results of these experiments are normally available fromthe manufacturer and they should be consulted by 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 manu
40、facturers instructions for use. Ingeneral, the following steps are involved:9.2.1.1 Open the sampler container at the time sampling isto be 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.
41、3 Record the start time.9.2.1.4 Record all pertinent information such as tempera-ture, barometric pressure, relative humidity, ambient air 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 instructi
42、ons for handlingand sealing the sampler, and record the end time. Submit thesamples to a laboratory for analysis or perform any on-siteread-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.Ensur
43、e 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, position the sampler at thedesired point. Ensure that the ambient air velocity at thesampler position is above the minimum velocity recommendedby the manufacturer.9.3
44、 Sampling Time:9.3.1 The minimum sampling time is governed by thesampling rate and by the sensitivity of the analytical method.Consult the manufacturers instructions for the appropriateminimum recommended sampling time.9.3.2 The maximum sampling time is governed by thesampling rate and by the capaci
45、ty of the sampler. Consult themanufacturers instructions for the maximum recommendedsampling time.9.3.2.1 When the maximum recommended sampling 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
46、 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 blank 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
47、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 contamination, thesamples taken must be assumed to be contaminated andappropriate action taken.9.4.2 Media blanks are unopened samplers that are alsosubmitted for anal
48、ysis. These need not be taken into the field.The results are used to correct sample results. Include approxi-mately five media blanks with each sample set. Consult themanufacturers instructions for the appropriate number.10. Handling and Shipping of Samples10.1 Where samples are shipped to a laborat
49、ory for subse-quent analysis, take precautions to minimize sample losses andprevent extraneous contamination.10.1.1 Seal samples securely and identify 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 fuel) or to sampleloss from depressurization. It may be possible to secure thesamples by shipping in an airtight container which includes apackage of adsorbent. Do n
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