1、Designation: D 3686 95 (Reapproved 2001)e1Standard Practice forSampling Atmospheres to Collect Organic CompoundVapors (Activated Charcoal Tube Adsorption Method)1This standard is issued under the fixed designation D 3686; the number immediately following the designation indicates the year oforiginal
2、 adoption or, in the case 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.e1NOTESI statement was added and part of Footnote F of Table A1.1 was deleted
3、editorially in October 2001.1. Scope1.1 This practice covers a method for the sampling ofatmospheres for determining the presence of certain organicvapors by means of adsorption on activated charcoal using acharcoal tube and a small portable sampling pump worn by aworker. A list of some of the organ
4、ic chemical vapors that canbe sampled by this practice is provided in Annex A1. This listis presented as a guide and should not be considered asabsolute or complete.1.2 This practice does not cover any method of samplingthat requires special impregnation of activated charcoal orother adsorption medi
5、a.1.3 The values stated in SI units are to be regarded as thestandard.1.4 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
6、 applica-bility of regulatory limitations prior to use. A specific safetyprecaution is given in 9.4.2. Referenced Documents2.1 ASTM Standards:D 1356 Terminology Relating to Sampling and Analysis ofAtmospheres2D 3687 Practice for Analysis of Organic Compound VaporsCollected by the Activated Charcoal
7、Tube AdsorptionMethod22.2 NIOSH Standard:CDC-99-74-45 Documentation of NIOSH Validation Tests3HSM-99-71-31 Personnel Sampler Pump for CharcoalTubes; Final Report32.3 OSHA Standard:CFR 1910 General Industrial OSHA Safety and HealthStandard43. Terminology3.1 For definitions of terms used in this metho
8、d, refer toTerminology D 1356.3.2 Activated charcoal refers to properly conditionedcoconut-shell charcoal.4. Summary of Practice4.1 Air samples are collected for organic vapor analysis byaspirating air at a known rate through sampling tubes contain-ing activated charcoal, which adsorbs the vapors.4.
9、2 Instructions are given to enable the laboratory personnelto assemble charcoal tubes suitable for sampling purposes.4.3 Instructions are given for calibration of the low flow-rate sampling pumps required in this practice.4.4 Information on the correct use of sampling devices ispresented.4.5 Practic
10、e D 3687 describes a practice for the analysis ofthese samples.5. Significance and Use5.1 Promulgations by the Federal Occupational Safety andHealth Administration (OSHA) in 29 CFR 1910.1000 desig-nate that certain organic compounds must not be present inworkplace atmospheres at concentrations above
11、 specific val-ues.5.2 This practice, when used in conjunction with PracticeD 3687, will provide the needed accuracy and precision in thedetermination of airborne time-weighted average concentra-tions of many of the organic chemicals given in 29CFR 1910.1000, CDC-99-74-45 and HSM-99-71-31.1This pract
12、ice is under the jurisdiction of ASTM Committee D22 on Air Qualityand is the direct responsibility of Subcommittee D22.04 on WorkplaceAtmospheres.Current edition approved January 15, 1995. Published March 1995. Originallypublished as D 3686 78. Last previous edition D 3686 89.2Annual Book of ASTM St
13、andards, Vol 11.03.3Available from the U.S. Department of Commerce, National Technical Infor-mation Service, Port Royal Road, Springfield, VA 22161.4Available from Superintendent of Documents, U.S. Government PrintingOffice, Washington, DC 20402.1Copyright ASTM International, 100 Barr Harbor Drive,
14、PO Box C700, West Conshohocken, PA 19428-2959, United States.5.3 A partial list of chemicals for which this method isapplicable is given in Annex A1, along with their OSHApermissible exposure limits.6. Interferences6.1 Water mist and vapor can interfere with the collection oforganic compound vapors.
15、 Humidity greater than 60 % canreduce the adsorptive capacity of activated charcoal to 50 %for some chemicals (1).5Presence of condensed water dropletsin the sample tube will indicate a suspect sample.7. Apparatus7.1 Charcoal Tube:7.1.1 A sampling tube consists of a length of glass tubingcontaining
16、two sections of activated charcoal which are held inplace by nonadsorbent material and sealed at each end.7.1.1.1 Sampling tubes are commercially available. Thetubes range in size from 100/50 to 800/400 mg, which meansthe tubes are divided into two sections with the front sectioncontaining 100 to 80
17、0 mg of activated charcoal and the backsection containing 50 to 400 mg of activated charcoal. The100/50-mg tube (2-4) and Fig. 1) which is the one mostfrequently used, consists of a glass tube, 70-mm long, 6-mmoutside diameter, 4-mm inside diameter, and contains twosections of 20/40 mesh-activated c
18、harcoal but separated by a2-mm section of urethane foam. The front section of 100 mg isretained by a plug of glass wool, and the back section of 50 mgis retained by either a second 2-mm portion of urethane foamor a plug of glass wool. Both ends of the tube are flame-sealed.NOTE 1Urethane foam is kno
19、wn to adsorb certain pesticides (5), forwhich this practice is contraindicated.7.1.1.2 When it is desirable to sample highly volatilecompounds for extended periods, or at a high volume flow rate,a larger device capable of efficient collection can be used,provided the proportions of the tube and its
20、charcoal contentsare scaled similarly to the base dimensions, to provide nomi-nally the same linear flow rate and contact time with thecharcoal bed.7.1.2 The back portion of the sampler tube, which maycontain between 25 and 100 % of the mass of activatedcharcoal present in the front section, adsorbs
21、 vapors thatpenetrate the front section and serves as a warning thatbreakthrough may have occurred. (Annex A1 gives recom-mended maximum tube loading information for many chemi-cals.)7.1.2.1 Should analysis of the back portion show it tocontain more than 10 % of the amount found in the frontsection,
22、 the possibility exists that solvent vapor penetrated bothsections of charcoal, and the sample must be consideredsuspect. These percentages apply to 100/50-mg tubes. Forother size tubes having disproportionate amounts of charcoal inthe front and back sections, the percentages used to indicatepotenti
23、al breakthrough must be adjusted to take into accountdifferent ratios of charcoal. If results from the analysis ofsuspect samples are used to calculate vapor concentrations, theresults must be reported as equal to or greater than thecalculated concentrations. In such cases, the test must berepeated
24、for confirmation of vapor concentration.NOTE 2Reportings from suspect samples would have significancewhen health standards are clearly exceeded and the amount by which theyare exceeded is academic. (See 9.5.)7.1.3 The adsorptive capacity and desorption efficiency ofdifferent batches of activated cha
25、rcoal may vary. Commercialtubes, if used, should be purchased from the same batch and insufficient number to provide sampling capacity for a definiteperiod of time. Care must be taken to have enough tubes fromthe same batch for a given study.7.1.3.1 The desorption efficiency and contamination level
26、ofa batch of tubes should be determined, following the procedureoutlined in Practice D 3687 for activated charcoal. A randomselection of at least five charcoal tubes from a specified lotshould be taken for these checks.7.1.4 Pressure drop across the sampling tube should be lessthan 25 mm Hg (3.3 kPa
27、) at a flow rate of 1000 mL/min andless than 4.6 mm Hg (0.61 kPa) at a flow rate of 200 mL/min.7.1.5 Charcoal sampling tubes prepared in accordance withthis practice and with sealed glass ends may be storedindefinitely.7.2 Sampling Pumps:7.2.1 Any pump whose flow rate can be accurately deter-mined a
28、nd be set at the desired sampling rate is suitable.Primarily though, this practice is intended for use with smallpersonal sampling pumps.7.2.2 Pumps having stable low flow rates (10 to 200mL/min) are preferable for long period sampling (up to 8 h) or5The boldface numbers in parentheses refer to the
29、list of references at the end ofthis standard.FIG. 1 Activated Charcoal Adsorption Sampling TubeD 3686 95 (2001)e12when the concentration of organic vapors is expected to behigh. Reduced sample volumes will prevent exceeding theadsorptive capacity of the charcoal tubes. (Suggested flow ratesand samp
30、ling times are given in Annex A1 for anticipatedconcentration ranges. Sample volumes are also discussed in9.5.)7.2.3 Pumps are available that will provide stable flow ratesbetween 6 5 %. Pumps should be calibrated before and aftersampling. If possible, flow rates should be checked during thecourse o
31、f the sampling procedure.7.2.4 All sampling pumps must be carefully calibrated withthe charcoal tube device in the proper sampling position. (SeeAnnex A2 for calibration procedure.)8. Reagents8.1 Activated Coconut-Shell CharcoalPrior to being usedto make sampling devices the charcoal should be heate
32、d in aninert gas to 600C and held there for 1 h. Commerciallyavailable coconut charcoal (20/40 mesh) has been found tohave adequate adsorption capacity. Other charcoals can be usedfor special applications.9. Sampling with Activated Charcoal Samplers9.1 Calibration of the Sampling SystemCalibrate the
33、 sam-pling system, including pump, flow regulator, tubing to beused, and a representative charcoal tube (or an equivalentinduced resistance) with a primary or calibrated secondaryflow-rate standard to 6 5%.9.1.1 Aprimary standard practice is given for the calibrationof low flow-rate pumps in Annex A
34、2 and Fig. A2.1.9.2 Break open both ends of the charcoal tube to be used forsampling, ensuring that each opening is at least one half theinside diameter of the tube.9.3 Insert the charcoal tube into the sampling line, placingthe back-up section nearest to the pump. At no time shouldthere be any tubi
35、ng ahead of the sampling tubes.9.4 For a breathing zone sample, fasten the sampling pumpto the worker, and attach the sampling tube as close to theworkers breathing zone as possible. Position the tube in avertical position to avoid channeling of air through the ad-sorber sections.NOTE 3Warning: Assu
36、re that the presence of the sampling equip-ment is not a safety hazard to the worker.9.4.1 Turn on the pump and adjust the flow rate to therecommended sampling rate.9.4.2 Record the flow rate and starting time or, dependingon the make of pump used, the register reading.9.5 Sampling VolumesThe minimu
37、m sample volume willbe governed by the detection limit of the analytical method,and the maximum sample volume will be determined by eitherthe adsorptive capacity of the charcoal or limitations of thepump battery.9.5.1 One method of calculating required sample volumes isto determine first the concent
38、ration range, over which it isimportant to report an exact number, for example from 0.2 to2 times the permissible exposure concentration, and thencalculate the sample volumes as follows:Minimum sample volume, m3(1)5minimum detection limit, mg0.2 3 permissible exposure limit, mg/m3Maximum sample volu
39、me, m3(2)5tube capacity for vapors, mg2 3 permissible exposure limit, mg/m39.5.2 Select a sampling rate that, in the sampling timedesired, will result in a sample volume between the minimumand maximum calculated in 9.5.1.9.5.2.1 Generally a long sampling time at a low flow rate ispreferable to short
40、-term high-volume sampling. This is consis-tent with the fact that most health standards are based on8-h/day time-weighted averages of exposure concentrations.9.5.2.2 Asample flow rate of less than 10 mL/min, however,should not be used. Calculations based upon diffusion coeffi-cients for several rep
41、resentative compounds indicate thatsampling at less than 10 mL/min may not give accurateresults.69.5.2.3 Approximate sample volumes and sample times aregiven in Annex A1.9.5.3 When spot checks are being made of an environment,a sample volume of 10 L is adequate for determining vaporconcentrations in
42、 accordance with exposure guidelines.9.6 At the end of the sampling period recheck the flow rate,turn off the pump, and record all pertinent information: time,register reading, and if pertinent, temperature, barometricpressure, and relative humidity.9.6.1 Seal the charcoal tube with the plastic caps
43、 provided.9.6.2 Label the tube with the appropriate information toidentify it.9.7 At least one charcoal sampling tube should be presentedfor analysis as a field blank with every 10 or 15 samples, or foreach specific inspection or field study.9.7.1 Break the sealed ends off the tube and cap it with t
44、heplastic caps. Do not draw air through the tube, but in all otherways treat it as an air sample.9.7.2 The purpose of the field blank is to assure that if thesampling tubes adsorb vapors extraneous to the samplingatmosphere, the presence of the contaminant will be detected.9.7.3 Results from the fie
45、ld blanks shall not be used tocorrect sample results. If a field blank shows contamination,the samples taken during the test must be assumed to becontaminated.9.8 Calculation of Sample Volume:9.8.1 For sample pumps with flow-rate meters:Sample volume, mL 5 f 3 t SP1P23T2T1D (3)where:f = flow rate sa
46、mpled, mL/min,t = sample time, min,P1= pressure during calibration of sampling pump (mm Hgor kPa)6Heitbrink, W. A., “Diffusion Effects Under Low Flow Conditions,” AmericanIndustrial Hygiene Association Journal, Vol 44, No. 6, 1983, pp. 453462.D 3686 95 (2001)e13P2= pressure of air sampled (mm Hg or
47、kPa)T1= temperature during calibration of sampling pump (K),andT2= temperature of air sampled (K).9.8.2 For sample pumps with counters:V 5R22 R1! 3 VI3P17603298T11 273(4)where:R2= final counter reading,R1= beginning counter reading,V = volume, (1) mL-count (1)P1= barometric pressure, mm Hg,T1= tempe
48、rature, C, andV = total sample volume, mL.10. Handling and Shipping of Samples Collected onCharcoal Sampling Tubes10.1 There is a paucity of information on the possible fate ofthe many different chemical species that can be collected inactivated charcoal and the variety of conditions to which theses
49、amples may be exposed. Good practice suggests the follow-ing:710.1.1 Samples should be capped securely and identifiedclearly.10.1.2 Samples collected in charcoal tubes should not bekept in warm places or exposed to direct sunlight.10.1.3 Samples of highly vaporous or low-boiling materials,such as vinyl chloride, should be stored and transported in dryice.10.1.4 At present there are no published test data on theeffect of conditions in aircraft cargo holds on capped samples.The preferred procedure is to carry the samples on board.10.1.5 Samples should be shipped as soon
