ASTM D4490-96
(Practice)Standard Practice for Measuring the Concentration of Toxic Gases or Vapors Using Detector Tubes
Standard Practice for Measuring the Concentration of Toxic Gases or Vapors Using Detector Tubes
SCOPE
1.1 This practice covers the detection and measurement of concentrations of toxic gases or vapors using detector tubes (1, 2). A list of some of the gases and vapors that can be detected by this practice is provided in Annex A1. This list is given as a guide and should be considered neither absolute nor complete.
1.2 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.
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Designation: D 4490 – 96 An American National Standard
Standard Practice for
Measuring the Concentration of Toxic Gases or Vapors
Using Detector Tubes
This standard is issued under the fixed designation D 4490; 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 designed is present, the indicator chemical in the tube will
change color (stain). The concentration of the gas or vapor may
1.1 This practice covers the detection and measurement of
be estimated by either (a) the length-of-stain compared to a
concentrations of toxic gases or vapors using detector tubes (1,
calibration chart, or (b) the intensity of the color change
2). A list of some of the gases and vapors that can be detected
compared to a set of standards.
by this practice, their 1994–95 TLV values recommended by
4.1.2 Long-Term Active Sampling (Long-Term Tubes) (19-
the ACGIH, and their measurement ranges are provided in
22)—A sample is pulled through the detector tube at a slow,
Annex A1. This list is given as a guide and should be
constant flow rate by an electrical pump. The time-weighted
considered neither absolute nor complete.
average concentration of the gas or vapor is determined by
1.2 This standard does not purport to address all of the
correlating the time of sampling either with (a) the length-of-
safety concerns, if any, associated with its use. It is the
stain read directly from the calibration curve imprinted on the
responsibility of the user of this standard to establish appro-
tube or ( b) the intensity of the color change compared to a set
priate safety and health practices and determine the applica-
of standards.
bility of regulatory limitations prior to use.
4.1.3 Long-Term Passive Sampling (Diffusion or Dosimeter
2. Referenced Documents
Tubes) (25)—The contaminant molecules move into the tube
according to Fick’s First Law of Diffusion. The driving force is
2.1 ASTM Standards:
the concentration differential between the ambient air and the
D 1356 Terminology Relating to Sampling and Analysis of
inside of the tube. The time-weighted average concentration of
Atmospheres
the gas or vapor is determined by dividing the indication on the
2.2 Other Document:
tube by the number of hours sampled (1 to 10 h according to
29 CFR 1910 Federal Occupational Safety and Health
the manufacturers’ instructions).
Standard Title 29
4.2 Instructions are given for the calibration of the sampling
3. Terminology
pumps required in this practice.
4.3 Information on the correct use of the detector tubes is
3.1 For definitions of terms used in this method, refer to
presented.
Terminology D 1356.
5. Significance and Use
4. Summary of Practice (3)
5.1 The Federal Occupational Safety and Health Adminis-
4.1 Detector tubes may be used for either short-term sam-
tration, in 29 CFR 1910, designates that certain gases and
pling (grab sampling; 1 to 10 min typically) or long term
vapors must not be present in workplace atmospheres at
sampling (actively or passively; 1 to 8 h) of atmospheres
concentrations above specific values.
containing toxic gases or vapors.
5.2 This practice will provide a means for the determination
4.1.1 Short-Term Sampling (Grab Sampling) (4-18)—A
of airborne concentrations of certain gases and vapors given in
given volume of air is pulled through the tube by a mechanical
29 CFR 1910.
pump. If the substance for which the detector tube was
5.3 A partial list of chemicals for which this practice is
applicable is presented in Annex A1.
This practice is under the jurisdiction of ASTM Committee D22 on Sampling
5.4 This practice also provides for the sampling of gaseous
and Analysis of Atmospheres and is the direct responsibility of Subcommittee
atmospheres to be used for process control or other purposes
D22.04 on Workplace Atmospheres.
Current edition approved Oct. 10, 1996. Published December 1996. Originally
(2, 23-25).
published as D 4490 – 85. Last previous edition D 4490 – 90.
The boldface numbers in parentheses refer to the list of references at the end of
6. Interferences (26, 27)
this practice.
Annual Book of ASTM Standards, Vol 11.03. 6.1 Some common interferences for the various tubes are
Code of Federal Regulations, Part 1910.1000 Subpart 2 and Part 1926.55
listed in the instruction sheets provided by the manufacturers.
Subpart D.
Copyright © ASTM, 100 Barr Harbor Drive, West Conshohocken, PA 19428-2959, United States.
D 4490
7. Apparatus (28-31) the other end of the tubing. This is useful for sampling in
inaccessible or dangerous places.
7.1 Detector Tube—A detector tube consists of a glass tube
7.3.5 Cooling Unit—The cooling unit consists of a length of
containing an inert granular material that has been impregnated
metal tubing through which the sampled gas is pulled. Because
with a chemical system which reacts with the gas or vapor of
of the high thermal conductivity of the metal tubing, the hot
interest. As a result of this reaction, the impregnated chemical
sampling gas is cooled sufficiently so that it will not destroy the
changes color. The granular material is held in place within the
indicator in the detector tube. The cooling unit must be placed
glass tube by porous plugs of a suitable inert material. The ends
upstream from the detector tube. Cooling units are particularly
of the glass tube are flame-sealed to protect the contents during
useful when sampling flue gases.
storage.
7.2 Pump (32):
8. Reagents
7.2.1 Short-Term Sampling—A mechanical, hand-operated,
8.1 The reagents used are specific for each tube, and, to
aspirating pump is used to draw the sample through the
detect a specific gas, may vary from manufacturer to manufac-
detector tube during the short-term sampling. Two types of
turer. The instruction sheets supplied by the manufacturers give
pumps are commercially available: piston-operated and
the principal chemical reaction(s) that occur(s) in the tube, thus
bellows-operated. The pumps have a capacity of 100 mL for a
showing the reagent that is used to react with the gas or vapor
full pump stroke. By varying the number of pump strokes, the
to produce the color change.
sample volume is controlled. Sampling pumps should be
maintained and calibration checked periodically according to 9. Sampling with Detector Tubes
the manufacturer’s instructions. The pumps shall be accurate to
9.1 General—Detector tubes made by one manufacturer
65 % of the volume stated.
must not be used with pumps made by a different manufacturer
7.2.2 Long-Term Sampling—Small electrical pumps having
(33). Each lot of detector tubes is calibrated at the manufac-
stable low flow rates (2 to 50 mL/min), are required for
turer’s plant, using their equipment. The pumps of other
long-term sampling (2 to 8 h). Flow rates to be used with each
manufacturers have different flow characteristics that cause
detector tube are given by the manufacturers. As with the
different lengths-of-stain resulting in erroneous readings.
mechanical pumps, the electrical pumps must be maintained
9.2 Procedure (34)—The detector tube program should be
and calibrated regularly. Maintenance and calibration are
conducted under the supervision of a trained professional such
performed using the instructions supplied by the manufacturer
as a chemist or an industrial hygienist. Carefully follow the
of the pump. The pump flow rate, and, therefore, the sampled
instruction sheet of the manufacturer for the proper use of each
volume, shall be accurate to 65 % of the stated flow rate. With
detector tube. In general, the instruction sheet will include the
this system either area or personal monitoring can be accom-
following information.
plished.
9.2.1 Storage conditions.
7.3 Accessories—Several accessories are provided with de-
9.2.2 Shelf life.
tector tubes for special applications:
9.2.3 Chemical reaction and color change.
7.3.1 Reactor Tubes—These are tubes that are used in
9.2.4 Test procedure.
conjunction with detector tubes. Some gases and vapors,
9.2.5 Significant interferences.
because of their low reactivity, are not easily detected by
9.2.6 Temperature and humidity correction factors, if re-
detector tubes alone. The reactor tubes consist of very powerful
quired.
chemical reactants, which break down the unreactive com-
9.2.7 Correction for atmospheric pressure.
pound into other more readily detectable substances, which
9.2.8 Measurement range.
standard detector tubes can detect. Thus, the reactor tube is
10. Accuracy of Detector Tubes
placed upstream of the detector tube and the combination must
be used for certain compounds as a detector tube system. 10.1 The Safety Equipment Institute (SEI) has a certifica-
tion program for certain detector tubes used in short-term
7.3.2 Dryer Tubes—Water vapor interferes with the detec-
sampling. This program is similar to the NIOSH program for
tion of certain substances; therefore, dryer tubes are used
evaluating and certifying detector tube performance (35, 36).
upstream of the detector tube in these cases to remove the
Under this program the tubes are required to meet an accuracy
water vapor.
(95 % confidence level) of 625 % between one and five times
7.3.3 Pyrolyzer—A pyrolyzer is a hot wire instrument
the SEI test concentration and 635 % at one half the test
operated by batteries. Instructions for its use and maintenance
concentration. The SEI test concentration is chosen as the
are given in the manufacturers’ instruction manuals. The
Threshold Limit Value as defined by the American Conference
purpose of the pyrolyzer, as with reactor tubes, is to break
of Governmental Industrial Hygienists for the test gas or vapor
down difficult-to-detect compounds into other compounds
(37). The calculation of tube accuracy is based on a set of
more easily detected. The breakdown in this case is caused by
statistical procedures (38) and provides an estimate of accuracy
heat. The pyrolzyer is particularly useful for organic nitrogen
under actual use conditions. The SEI Certifi
...
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