ASTM D4597-97
(Practice)Standard Practice for Sampling Workplace Atmospheres to Collect Gases or Vapors with Solid Sorbent Diffusive Samplers
Standard Practice for Sampling Workplace Atmospheres to Collect Gases or Vapors with Solid Sorbent Diffusive Samplers
SCOPE
1.1 This practice covers the sampling of workplace atmospheres for the presence of certain vapors or gases by means of diffusion across a specified quiescent region and subsequent adsorption on a solid sorbent.
General Information
Relations
Standards Content (Sample)
NOTICE: This standard has either been superceded and replaced by a new version or discontinued.
Contact ASTM International (www.astm.org) for the latest information.
Designation: D 4597 – 97
Standard Practice for
Sampling Workplace Atmospheres to Collect Gases or
Vapors with Solid Sorbent Diffusive Samplers
This standard is issued under the fixed designation D 4597; 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 2.2 Other Document:
Title 29CFR 1910.1000 Subpart Z Occupational Health and
1.1 This practice covers the sampling of workplace atmo-
Safety Standard
spheres for the presence of certain gases or vapors by means of
diffusion across a specified quiescent region and subsequent
3. Terminology
sorption on a solid sorbent (1).
3.1 Terminology D 1356 contains definitions of terms used
1.2 A list of organic compounds which are applicable to
in this practice.
solid sorbent sampling where the sorbent is contained in a bed
3.2 Definitions of Terms Specific to This Standard:
through which air is passed is given in Annex A1 of Practice
3.2.1 diffusion—the movement of gas or vapor molecules
D 3686. Diffusive samplers may be applicable to a similar
from a region of high concentration to a region of low
range of compounds but this must be confirmed by reference to
concentration as described by Fick’s first law (8.1).
the individual sampler manufacturers’ literature.
3.2.2 diffusive sampler—assembly used for sampling gas or
1.3 The valid use of diffusive samplers depends on the
vapor molecules from the atmosphere.
existence of actual laboratory or field validation, or both.
3.2.3 sampling rate—the ratio of mass of a given compound
Guidance on validation can be obtained from published proto-
collected by a diffusive sampler per unit time of exposure to the
cols (2-6). This practice is not designed to cover the verifica-
concentration of that compound in the atmosphere being
tion, validation, or specific test procedures used to assess the
sampled. The sampling rate is sometimes referred to as the
accuracy or precision of diffusive samplers.
uptake rate. Units are ng (or mg) mg/m /min (or h), which are
1.4 This standard does not purport to address all of the
dimensionally equivalent to a volume flow-rate (for example
safety concerns, if any, associated with its use. It is the
cm /min).
responsibility of the user of this standard to establish appro-
priate safety and health practices and determine the applica-
4. Summary of Practice
bility of regulatory limitations prior to use.
4.1 Molecules are sampled from the atmosphere by a
2. Referenced Documents diffusive sampler. During the sampling process, the molecules
diffuse from the environment adjacent to the sampler through
2.1 ASTM Standards:
a region of defined geometric structure and into a region
D 1356 Terminology Relating to Sampling and Analysis of
3 containing the sorbent medium. The theory of diffusive sam-
Atmospheres
pling is given in this practice.
D 3686 Practice for Sampling Atmospheres to Collect Or-
4.2 Instructions are given for the correct use of the sampling
ganic Compound Vapors (Activated Charcoal Tube Ad-
3 devices to enable their field application.
sorption Method)
4.3 Information on the calculation of environmental concen-
D 3687 Practice for Analysis of Organic Compound Vapors
tration based on sampler assay is given.
Collected by the Activated Charcoal Tube Adsorption
Method
5. Significance and Use
5.1 Promulgations by the Federal Occupational Safety and
Health Administration in 29 CFR 1910.1000 designate that
This practice is under the jurisdiction of ASTM Committee D-22 on Sampling
certain hazardous gases and vapors must not be present in the
and Analysis of Atmospheres and is the direct responsibility of Subcommittee
workplace air at concentrations above specific values.
D22.04 on Workplace Atmospheres.
5.2 This practice, when used in conjunction with an analyti-
Current edition approved Sept. 10, 1997. Published December 1997. Originally
published as D 4597 – 87. Last previous edition D 4597 – 92.
cal technique, such as that given for organic compounds in
The boldface numbers in parentheses refer to the list of references at the end of
this practice.
Annual Book of ASTM Standards, Vol 11.03.
Code of Federal Regulations, available from U.S. Government Printing Office,
Washington, DC 20402.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
NOTICE: This standard has either been superceded and replaced by a new version or discontinued.
Contact ASTM International (www.astm.org) for the latest information.
D 4597
Practice D 3687, may provide a means for the determination of 8. Diffusive Sampling Theory
time-weighted airborne concentrations of many of the hazard-
8.1 Fick’s first law of diffusion states that for a constant
ous gases and vapors in 29CFR 1919.1000, as well as others.
concentration gradient, the mass of material transferred to the
5.3 The manufacturer’s literature should be consulted for
sampling layer can be expressed as follows:
the appropriate list of chemicals which may be sampled by a
DA
particular device.
M 5 ~C 2 C !t (1)
o
L
6. Interferences
where:
6.1 The diffusive sampling process can be jeopardized by
M = mass of material, ng,
physical blockage of entrances to the interior of the device such
D = diffusion co-efficient, cm /min (Note 1),
as by liquid droplets or dust particles. A = cross sectional area of diffusion cavity(ies), cm (Note
6.2 The diffusive sampling process can be jeopardized by 2),
L = length of diffusion path, cm (Note 3),
structural damage to any membranes or other elements used to
C = gas phase concentration at face of sampler, ng/cm ,
control either the geometry of the diffusion path or turbulence
C = gas phase concentration at sorbent surface, ng/cm ,
within the diffusion path. o
and
6.3 The diffusive sampling process can be jeopardized by
t = exposure time, min.
air movement within the diffusion path. Recent sampler de-
signs have incorporated elements to decrease this possibility.
NOTE 1—The diffusion coefficient of a molecule is a function of the
6.4 The diffusive sampling process can be jeopardized by temperature and the nature of the medium through which it is diffusing.
Should the medium be a compressible fluid (for example, air) the diffusion
insufficient mixing of the air external to the sampler. This is
coefficient will also be a function of the pressure.
known as starvation. The manufacturer should provide a
NOTE 2—The presence of barriers to the entry of external air move-
recommended minimum ambient air velocity, below which the
ments may alter the effective cross-sectional area of the sampler.
sampler should not be used.
NOTE 3—Under certain circumstances the length of the diffusion path
6.5 The diffusive sampling process can be jeopardized if the
can be significantly extended into the thickness of the sorbent layer during
concentration in air at the sorbent interface becomes sufficient
sampling. Certain types of sampler make use of this phenomenon to give
to significantly alter the diffusion gradient within the diffusion
a length of stain read-out. In this situation, the mathematical treatment of
path. This can occur through sorbent saturation, either from the
Fick’s law is more complex than that given here.
presence of competing species (which may include water vapor
8.2 The sampling rate (SR) of a diffusive sampler for a
molecules), or the selection of an inappropriate sorbent mate-
specific gas or vapor may be expressed as follows:
rial for the concentration and time of exposure, or by increased
DA M
temperature. The manufacturer should provide, or the user
SR 5 5 (2)
L
~C 2 C !t
should determine, the range of conditions over which signifi- o
cant bias from sorbent saturation will not occur.
where:
6.6 Errors may arise in estimating exposure using diffusive 3
SR = sampling rate, cm /min.
samplers in instances in which the concentration of the gas or
where:
vapor being sampled varies significantly over time.
concentration (C, C ) is given in ppm (v/v) the units of SR
o
6.7 Where multiple gases or vapors are sampled simulta-
become ng/ppm/min.
neously, care must be exercised to ensure there is no mutual
8.2.1 Sampling rates may be estimated from diffusion coef-
interference in the analytical method chosen.
ficient ratios if the sampling rate of one substance is known:
7. Apparatus SR
SR 5 D (3)
2 2
D
7.1 Diffusive Sampling Devices:
7.1.1 A diffusive sampler consists of a cavity or group of However, where diffusion coefficients are calculated values
cavities containing air and terminated at one end by a sorbent rather than measurements, the potential for error exists in this
substrate and opening at the other to the environment. The procedure. Where possible, sampling rates should be confirmed
cavity or group of cavities form a region of defined geometry by the results of experimental protocols.
which acts as a control on the rate of gaseous diffusion from the 8.2.2 The sampling rate for a gas or vapor through air is
1.5
theoretically proportional to T /P where T is the absolute
external environment to the sorbent substrate. Barriers to the
entry of external air movements are common. Samplers where temperature (in °K) and P is the pressure (in kPa) (7); while in
practice, the concomitant air volume changes result in apparent
the diffusion of gas or vapor is through materials other than air
are covered by this practice, but it should be noted that the sampling rate changes of 0.2 % per °K and virtually no
influence of temperature on diffusion may be more pro- pressure effects. However, the exposure limits given in 29CFR
nounced. 1910.1000 Subpart Z are referenced to standard temperature
7.1.2 Diffusive samplers are equipped with a means of and pressure (STP). Therefore, in order to compare a concen-
attachment to the body for personal sampling or to a suitable tration value (in ppm) from a diffu
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