ASTM D3686-95
(Practice)Standard Practice for Sampling Atmospheres to Collect Organic Compound Vapors (Activated Charcoal Tube Adsorption Method)
Standard Practice for Sampling Atmospheres to Collect Organic Compound Vapors (Activated Charcoal Tube Adsorption Method)
SCOPE
1.1 This practice covers a method for the sampling of atmospheres for determining the presence of certain organic vapors by means of adsorption on activated charcoal using a charcoal tube and a small portable sampling pump worn by a worker. A list of some of the organic chemical vapors that can be sampled by this practice is provided in Annex 1. This list is presented as a guide and should not be considered as absolute or complete.
1.2 This practice does not cover any method of sampling that requires special impregnation of activated charcoal or other adsorption media.
1.3 The values stated in SI units are to be regarded as the standard.
1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use. A specific safety precaution is given in .
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Designation: D 3686 – 95 An American National Standard
Standard Practice for
Sampling Atmospheres to Collect Organic Compound
Vapors (Activated Charcoal Tube Adsorption Method)
This standard is issued under the fixed designation D 3686; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (e) indicates an editorial change since the last revision or reapproval.
1. Scope 3. Terminology
1.1 This practice covers a method for the sampling of 3.1 For definitions of terms used in this method, refer to
atmospheres for determining the presence of certain organic Terminology D 1356.
vapors by means of adsorption on activated charcoal using a 3.2 Activated charcoal refers to properly conditioned
charcoal tube and a small portable sampling pump worn by a coconut-shell charcoal.
worker. A list of some of the organic chemical vapors that can
4. Summary of Practice
be sampled by this practice is provided in Annex A1. This list
4.1 Air samples are collected for organic vapor analysis by
is presented as a guide and should not be considered as
aspirating air at a known rate through sampling tubes contain-
absolute or complete.
1.2 This practice does not cover any method of sampling ing activated charcoal, which adsorbs the vapors.
4.2 Instructions are given to enable the laboratory personnel
that requires special impregnation of activated charcoal or
other adsorption media. to assemble charcoal tubes suitable for sampling purposes.
4.3 Instructions are given for calibration of the low flow-
1.3 This standard does not purport to address all of the
safety concerns, if any, associated with its use. It is the rate sampling pumps required in this practice.
4.4 Information on the correct use of sampling devices is
responsibility of the user of this standard to establish appro-
priate safety and health practices and determine the applica- presented.
4.5 Practice D 3687 describes a practice for the analysis of
bility of regulatory limitations prior to use. A specific safety
precaution is given in 9.4. these samples.
5. Significance and Use
2. Referenced Documents
2.1 ASTM Standards: 5.1 Promulgations by the Federal Occupational Safety and
Health Administration (OSHA) in 29 CFR 1910.1000 desig-
D 1356 Terminology Relating to Atmospheric Sampling
and Analysis of Atmospheres nate that certain organic compounds must not be present in
workplace atmospheres at concentrations above specific val-
D 3687 Practice for Analysis of Organic Compound Vapors
Collected by the Activated Charcoal Tube Adsorption ues.
5.2 This practice, when used in conjunction with Practice
Method
2.2 NIOSH Standard: D 3687, will provide the needed accuracy and precision in the
determination of airborne time-weighted average concentra-
CDC-99-74-45 Documentation of NIOSH Validation Tests
tions of many of the organic chemicals given in 29 CFR
HSM-99-71-31 Personnel Sampler Pump for Charcoal
Tubes; Final Report 1910.1000, CDC-99-74-45 and HSM-99-71-31.
5.3 A partial list of chemicals for which this method is
2.3 OSHA Standard:
CFR 1910 General Industrial OSHA Safety and Health applicable is given in Annex A1, along with their OSHA
permissible exposure limits.
Standard
6. Interferences
6.1 Water mist and vapor can interfere with the collection of
This practice is under the jurisdiction of ASTM Committee D-22 on Sampling
organic compound vapors. Humidity greater than 60 % can
and Analysis of Atmospheres, and is the direct responsibility of Subcommittee
reduce the adsorptive capacity of activated charcoal to 50 %
D22.04on Analysis of Workplace Atmospheres.
for some chemicals (1). Presence of condensed water droplets
Current edition approved Jan. 15, 1995. Published March 1995. Originally
published as D 3686 – 78. Last previous edition D 3686 – 89. in the sample tube will indicate a suspect sample.
Annual Book of ASTM Standards, Vol 11.03.
Available from the U.S. Department of Commerce, National Technical Infor-
mation Service, Port Royal Road, Springfield, VA 22161.
Available from Superintendent of Documents, U.S. Government Printing
The boldface numbers in parentheses refer to the list of references at the end of
Office, Washington, DC 20402.
this standard.
Copyright © ASTM, 100 Barr Harbor Drive, West Conshohocken, PA 19428-2959, United States.
D 3686
7. Apparatus results must be reported as equal to or greater than the
calculated concentrations. In such cases, the test must be
7.1 Charcoal Tube:
repeated for confirmation of vapor concentration.
7.1.1 A sampling tube consists of a length of glass tubing
containing two sections of activated charcoal which are held in
NOTE 2—Reportings from suspect samples would have significance
place by nonadsorbant material and sealed at each end.
when health standards are clearly exceeded and the amount by which they
7.1.1.1 Sampling tubes are commercially available. The are exceeded is academic. (See 9.5.)
tubes range in size from 100/50 to 800/400 mg, which means
7.1.3 The adsorptive capacity and desorption efficiency of
the tubes are divided into two sections with the front section
different batches of activated charcoal may vary. Commercial
containing 100 to 800 mg of activated charcoal and the back
tubes, if used, should be purchased from the same batch and in
section containing 50 to 400 mg of activated charcoal. The
sufficient number to provide sampling capacity for a definite
100/50-mg tube ((2-4) and Fig. 1) which is the one most
period of time. Care must be taken to have enough tubes from
frequently used, consists of a glass tube, 70-mm long, 6-mm
the same batch for a given study.
outside diameter, 4-mm inside diameter, and contains two
7.1.3.1 The desorption efficiency and contamination level of
sections of 20/40 mesh-activated charcoal but separated by a
a batch of tubes should be determined, following the procedure
2-mm section of urethane foam. The front section of 100 mg is
outlined in Practice D 3687 for activated charcoal. A random
retained by a plug of glass wool, and the back section of 50 mg
selection of at least five charcoal tubes from a specified lot
is retained by either a second 2-mm portion of urethane foam
should be taken for these checks.
or a plug of glass wool. Both ends of the tube are flame-sealed.
7.1.4 Pressure drop across the sampling tube should be less
NOTE 1—Urethane foam is known to adsorb certain pesticides (5), for
than 25 mm Hg (3.3 kPa) at a flow rate of 1000 mL/min and
which this practice is contraindicated.
less than 4.6 mm Hg (0.61 kPa) at a flow rate of 200 mL/min.
7.1.1.2 When it is desirable to sample highly volatile
7.1.5 Charcoal sampling tubes prepared in accordance with
compounds for extended periods, or at a high volume flow rate,
this practice and with sealed glass ends may be stored
a larger device capable of efficient collection can be used,
indefinitely.
provided the proportions of the tube and its charcoal contents
7.2 Sampling Pumps:
are scaled similarly to the base dimensions, to provide nomi-
7.2.1 Any pump whose flow rate can be accurately deter-
nally the same linear flow rate and contact time with the
mined and be set at the desired sampling rate is suitable.
charcoal bed.
Primarily though, this practice is intended for use with small
7.1.2 The back portion of the sampler tube, which may
personal sampling pumps.
contain between 25 and 100 % of the mass of activated
7.2.2 Pumps having stable low flow rates (10 to 200
charcoal present in the front section, adsorbs vapors that
mL/min) are preferable for long period sampling (up to 8 h) or
penetrate the front section and serves as a warning that
when the concentration of organic vapors is expected to be
breakthrough may have occurred. (Annex A1 gives recom-
high. Reduced sample volumes will prevent exceeding the
mended maximum tube loading information for many chemi-
adsorptive capacity of the charcoal tubes. (Suggested flow rates
cals.)
and sampling times are given in Annex A1 for anticipated
7.1.2.1 Should analysis of the back portion show it to
concentration ranges. Sample volumes are also discussed in
contain more than 10 % of the amount found in the front
9.5.)
section, the possibility exists that solvent vapor penetrated both
7.2.3 Pumps are available that will provide stable flow rates
sections of charcoal, and the sample must be considered
between6 5 %. Pumps should be calibrated before and after
suspect. These percentages apply to 100/50-mg tubes. For
sampling. If possible, flow rates should be checked during the
other size tubes having disproportionate amounts of charcoal in
course of the sampling procedure.
the front and back sections, the percentages used to indicate
potential breakthrough must be adjusted to take into account 7.2.4 All sampling pumps must be carefully calibrated with
different ratios of charcoal. If results from the analysis of the charcoal tube device in the proper sampling position. (See
suspect samples are used to calculate vapor concentrations, the Annex A2 for calibration procedure.)
FIG. 1 Activated Charcoal Adsorption Sampling Tube
D 3686
8. Reagents 9.5.2.2 A sample flow rate of less than 10 mL/min, however,
should not be used. Calculations based upon diffusion coeffi-
8.1 Activated Coconut-Shell Charcoal—Prior to being used
cients for several representative compounds indicate that
to make sampling devices the charcoal should be heated in an
sampling at less than 10 mL/min may not give accurate
inert gas to 600°C and held there for 1 h. Commercially
results.
available coconut charcoal (20/40 mesh) has been found to
9.5.2.3 Approximate sample volumes and sample times are
have adequate adsorption capacity. Other charcoals can be used
given in Annex A1.
for special applications.
9.5.3 When spot checks are being made of an environment,
a sample volume of 10 L is adequate for determining vapor
9. Sampling with Activated Charcoal Samplers
concentrations in accordance with exposure guidelines.
9.1 Calibration of the Sampling System—Calibrate the sam-
9.6 At the end of the sampling period recheck the flow rate,
pling system, including pump, flow regulator, tubing to be
turn off the pump, and record all pertinent information: time,
used, and a representative charcoal tube (or an equivalent
register reading, and if pertinent, temperature, barometric
induced resistance) with a primary or calibrated secondary
pressure, and relative humidity.
flow-rate standard to 6 5%.
9.6.1 Seal the charcoal tube with the plastic caps provided.
9.1.1 A primary standard practice is given for the calibration
9.6.2 Label the tube with the appropriate information to
of low flow-rate pumps in Annex A2 and Fig. A2.1.
identify it.
9.2 Break open both ends of the charcoal tube to be used for
9.7 At least one charcoal sampling tube should be presented
sampling, ensuring that each opening is at least one half the
for analysis as a field blank with every 10 or 15 samples, or for
inside diameter of the tube.
each specific inspection or field study.
9.3 Insert the charcoal tube into the sampling line, placing
9.7.1 Break the sealed ends off the tube and cap it with the
the back-up section nearest to the pump. At no time should
plastic caps. Do not draw air through the tube, but in all other
there be any tubing ahead of the sampling tubes.
ways treat it as an air sample.
9.4 For a breathing zone sample, fasten the sampling pump
9.7.2 The purpose of the field blank is to assure that if the
to the worker, and attach the sampling tube as close to the
sampling tubes adsorb vapors extraneous to the sampling
worker’s breathing zone as possible. Position the tube in a
atmosphere, the presence of the contaminant will be detected.
vertical position to avoid channeling of air through the ad-
9.7.3 Results from the field blanks shall not be used to
sorber sections.
correct sample results. If a field blank shows contamination,
NOTE 3—Warning: Assure that the presence of the sampling equip-
the samples taken during the test must be assumed to be
ment is not a safety hazard to the worker.
contaminated.
9.8 Calculation of Sample Volume:
9.4.1 Turn on the pump and adjust the flow rate to the
recommended sampling rate. 9.8.1 For sample pumps with flow-rate meters:
9.4.2 Record the flow rate and starting time or, depending
P T
1 2
Sample volume, mL 5 f 3 t 3 (3)
on the make of pump used, the register reading. S˛ D
P T
2 1
9.5 Sampling Volumes—The minimum sample volume will
where:
be governed by the detection limit of the analytical method,
f 5 flow rate sampled, mL/min,
and the maximum sample volume will be determined by either
t 5 sample time, min,
the adsorptive capacity of the charcoal or limitations of the
P 5 pressure during calibration of sampling pump (mm Hg
pump battery. 1
or kPa)
9.5.1 One method of calculating required sample volumes is
P 5 pressure of air sampled (mm Hg or kPa)
to determine first the concentration range, over which it is
T 5 temperature during calibration of sampling pump (K),
important to report an exact number, for example from 0.2 to
and
2 times the permissible exposure concentration, and then
T 5 temperature of air sampled (K).
calculate the sample volumes as follows:
9.8.2 For sample pumps with counters:
Minimum sample volume, m (1)
~R 2 R ! 3 V P 298
2 1 1
V 5 3 3 (4)
minimum detection limit, mg
I 760 T 1 273
0.2 3 permissible exposure limit,mg/m
where:
Maximum sample volume, m (2)
R 5 final counter reading,
5 beginning counter reading,
tube capacity for vapors, mg R
V 5 volume, (1) mL-count (1)
2 3 permissible exposure limit, mg/m
P 5 barometric pressure, mm Hg,
9.5.2 Select a sampling rate that, in the sampling time
T 5 temperature, °C, and
desired, will result in a sample volume between the minimum
V 5 total sample volume, mL.
and maximum calculated in 9.5.1.
9.5.2.1 Generally a long sampling time at a low flow rate is
preferable to short-term high-volume sampling. This is consis-
tent with the fact that most health standards are based on
Heitbrink, W. A., “Diffusion Effects Under Low Flow Conditions,” American
8-h/day time-weighted averages of exposure concentrations. Industrial Hygiene Association Journal, Vol 44, No. 6, 1983, pp. 453–462.
D 3686
10. Handling and Shipping of Samples Collected on 10.1.4 At present there are no published test data on the
Charcoal Sampling Tubes effect of conditions in aircraft cargo holds on capped samples.
The preferred procedure is to carry the samples on board.
10.1 There is a paucity of information on the possible fate of
10.1.5 Samples should be s
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