ASTM D737-04(2008)e2
(Test Method)Standard Test Method for Air Permeability of Textile Fabrics
Standard Test Method for Air Permeability of Textile Fabrics
SIGNIFICANCE AND USE
This test method is considered satisfactory for acceptance testing of commercial shipments since current estimates of between-laboratory precision are acceptable, and this test method is used extensively in the trade for acceptance testing.
If there are differences of practical significance between reported test results for two laboratories (or more), comparative tests should be performed to determine if there is a statistical bias between them, using competent statistical assistance. As a minimum, ensure the test samples to be used are as homogeneous as possible, are drawn from the material from which the disparate test results were obtained, and are randomly assigned in equal number to each laboratory for testing. The test results from the two laboratories should be compared using a statistical test for unpaired data, at a probability level chosen prior to the testing series. If bias is found, either its cause must be found and corrected, or future test results for that material must be adjusted in consideration of the known bias.
Air permeability is an important factor in the performance of such textile materials as gas filters, fabrics for air bags, clothing, mosquito netting, parachutes, sails, tentage, and vacuum cleaners. In filtration, for example, efficiency is directly related to air permeability. Air permeability also can be used to provide an indication of the breathability of weather-resistant and rainproof fabrics, or of coated fabrics in general, and to detect changes during the manufacturing process.
Performance specifications, both industrial and military, have been prepared on the basis of air permeability and are used in the purchase of fabrics where permeability is of interest.
Construction factors and finishing techniques can have an appreciable effect upon air permeability by causing a change in the length of airflow paths through a fabric. Hot calendaring can be used to flatten fabric components, thus reducing air permeability. Fabrics...
SCOPE
1.1 This test method covers the measurement of the air permeability of textile fabrics.
1.2 This test method applies to most fabrics including woven fabrics, nonwoven fabrics, air bag fabrics, blankets, napped fabrics, knitted fabrics, layered fabrics, and pile fabrics. The fabrics may be untreated, heavily sized, coated, resin-treated, or otherwise treated.
1.3 The values stated in SI units are to be regarded as the standard. The values stated in inch-pound units may be approximate.
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.
General Information
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Standards Content (Sample)
NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
Designation:D737–04 (Reapproved 2008)
Standard Test Method for
Air Permeability of Textile Fabrics
This standard is issued under the fixed designation D737; 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 (´) indicates an editorial change since the last revision or reapproval.
This standard has been approved for use by agencies of the Department of Defense.
´ NOTE—Editorial changes were made in August 2008.
´ NOTE—In paragraph 6.1.4 the closing parenthesis was moved to follow “of water” in April 2011.
1. Scope F778 MethodsforGasFlowResistanceTestingofFiltration
Media
1.1 This test method covers the measurement of the air
permeability of textile fabrics.
3. Terminology
1.2 This test method applies to most fabrics including
3.1 For definition of textile terms used in this test method:
woven fabrics, nonwoven fabrics, air bag fabrics, blankets,
air permeability, and fabric, refer to Terminology D4850.
nappedfabrics,knittedfabrics,layeredfabrics,andpilefabrics.
3.2 For definitions of cross-machine direction; machine
The fabrics may be untreated, heavily sized, coated, resin-
direction and other textile terms used in this test method, refer
treated, or otherwise treated.
to Terminology D123.
1.3 The values stated in SI units are to be regarded as the
standard. The values stated in inch-pound units may be
4. Summary of Test Method
approximate.
4.1 The rate of air flow passing perpendicularly through a
1.4 This standard does not purport to address all of the
known area of fabric is adjusted to obtain a prescribed air
safety concerns, if any, associated with its use. It is the
pressure differential between the two fabric surfaces. From this
responsibility of the user of this standard to establish appro-
rate of air flow, the air permeability of the fabric is determined.
priate safety and health practices and determine the applica-
bility of regulatory limitations prior to use.
5. Significance and Use
5.1 This test method is considered satisfactory for accep-
2. Referenced Documents
2 tance testing of commercial shipments since current estimates
2.1 ASTM Standards:
of between-laboratory precision are acceptable, and this test
D123 Terminology Relating to Textiles
method is used extensively in the trade for acceptance testing.
D1776 Practice for Conditioning and Testing Textiles
5.1.1 If there are differences of practical significance be-
D2904 Practice for Interlaboratory Testing of a Textile Test
tween reported test results for two laboratories (or more),
Method that Produces Normally Distributed Data
comparative tests should be performed to determine if there is
D2906 Practice for Statements on Precision and Bias for
3 a statistical bias between them, using competent statistical
Textiles
assistance. As a minimum, ensure the test samples to be used
D4850 Terminology Relating to Fabrics and Fabric Test
are as homogeneous as possible, are drawn from the material
Methods
from which the disparate test results were obtained, and are
randomly assigned in equal number to each laboratory for
testing. The test results from the two laboratories should be
This test method is under the jurisdiction ofASTM Committee D13 onTextiles
compared using a statistical test for unpaired data, at a
and is the direct responsibility of Subcommittee D13.59 on Fabric Test Methods,
General. probability level chosen prior to the testing series. If bias is
Current edition approved July 1, 2008. Published August 2008. Originally
found, either its cause must be found and corrected, or future
approved in 1943 . Last previous edition approved in 2004 as D737 – 04. DOI:
test results for that material must be adjusted in consideration
10.1520/D0737-04R08E02.
of the known bias.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
5.2 Air permeability is an important factor in the perfor-
Standards volume information, refer to the standard’s Document Summary page on
mance of such textile materials as gas filters, fabrics for air
the ASTM website.
bags, clothing, mosquito netting, parachutes, sails, tentage, and
Withdrawn. The last approved version of this historical standard is referenced
on www.astm.org. vacuum cleaners. In filtration, for example, efficiency is
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
´2
D737–04 (2008)
directlyrelatedtoairpermeability.Airpermeabilityalsocanbe preferably provides pressure differentials of between 100 and
used to provide an indication of the breathability of weather- 2500 Pa (10 and 250 mm or 0.4 and 10 in. of water) between
resistant and rainproof fabrics, or of coated fabrics in general, the two surfaces of the fabric being tested. At a minimum, the
and to detect changes during the manufacturing process. test apparatus must provide a pressure drop of 125 Pa (12.7
5.3 Performance specifications, both industrial and military, mm or 0.5 in. of water) across the specimen.
have been prepared on the basis of air permeability and are 6.1.4 Pressure Gage or Manometer, connected to the test
used in the purchase of fabrics where permeability is of headunderneaththetestspecimentomeasurethepressuredrop
interest. across the test specimen in pascals (millimetres or inches of
5.4 Construction factors and finishing techniques can have water) with an accuracy of 62%.
anappreciableeffectuponairpermeabilitybycausingachange 6.1.5 Flowmeter, volumetric counter or measuring aperture
3 2
in the length of airflow paths through a fabric. Hot calendaring to measure air velocity through the test area in cm /s/cm
3 2
can be used to flatten fabric components, thus reducing air (ft /min/ft ) with an accuracy of 62%.
permeability. Fabrics with different surface textures on either 6.1.6 Calibration Plate, or other means, with a known air
side can have a different air permeability depending upon the permeabilityattheprescribedtestpressuredifferentialtoverify
direction of air flow. the apparatus.
5.4.1 Forwovenfabric,yarntwistalsoisimportant.Astwist 6.1.7 Means of calculating and displaying the required
increases, the circularity and density of the yarn increases, thus results, such as scales, digital display, and computer-driven
reducing the yarn diameter and the cover factor and increasing systems.
the air permeability.Yarn crimp and weave influence the shape 6.2 Cutting Dies or Templates, to cut specimens having
and area of the interstices between yarns and may permit yarns dimensions at least equal to the area of the clamping surfaces
toextendeasily. Such yarn extension would open upthefabric, of the test apparatus (optional).
increase the free area, and increase the air permeability.
7. Sampling and Test Specimens
5.4.2 Increasingyarntwistalsomayallowthemorecircular,
high-density yarns to be packed closely together in a tightly
7.1 Lot Sample—As a lot sample for acceptance testing,
woven structure with reduced air permeability. For example, a
randomly select the number of rolls or pieces of fabric directed
worsted gabardine fabric may have lower air permeability than
in an applicable material specification or other agreement
a woolen hopsacking fabric.
between the purchaser and the supplier. Consider the rolls or
pieces of fabric to be the primary sampling units. In the
6. Apparatus
absence of such an agreement, take the number of fabric rolls
6.1 Air Permeability Testing Apparatus consisting of the
or pieces specified in Table 1.
following:
NOTE 3—An adequate specification or other agreement between the
6.1.1 Test Head that provides a circular test area of 38.3
2 purchaser and the supplier requires taking into account the variability
cm (5.93 in. )6 0.3 %.
between rolls or pieces of fabric and between specimens from a swatch
2 2
fromarollorpieceoffabrictoprovideasamplingplanwithameaningful
NOTE 1—Alternate test areas may be used, such as 5 cm (0.75 in. ),
2 2 2 2
producer’s risk, consumer’s risk, acceptable quality level, and limiting
6.45 cm (1.0 in. ), and 100 cm (15.5 in. ).
quality level.
6.1.2 Clamping System to Secure Test Specimens, of differ-
7.2 Laboratory Sample—For acceptance testing, take a
ent thicknesses under a force of at least 50 65N(11 6 1 lbf)
swatch extending the width of the fabric and approximately 1
to the test head without distortion and minimal edge leakage
m (1 yd) along the lengthwise direction from each roll or piece
underneath the test specimen.
in the lot sample. For rolls of fabric, take a sample that will
6.1.2.1 Asuitable means to minimize edge leakage is to use
exclude fabric from the outer wrap of the roll or the inner wrap
a 55 Type A durometer hardness polychloroprene (neoprene)
around the core of the roll of fabric.
clamping ring 20 mm (0.75 in.) wide and 3 mm (0.125 in.)
7.3 Test Specimens—From each laboratory sampling unit,
thick around the test area above and underneath the test
take ten specimens unless otherwise agreed upon between
specimen.
purchaser and supplier. Use the cutting die or template de-
NOTE 2—Since air leakage may affect test results, precautions must be
scribed in 6.2, or if practical, make air permeability tests of a
taken, especially with very heavy or lofty fabrics, to prevent leakage. The
textile fabric without cutting.
use of a weighted ring and rubber gaskets on the clamp surfaces has been
7.3.1 Cutting Test Specimens—Whencuttingspecimens,cut
found to be helpful. Methods F778 describes a series of usable clamping
having dimensions at least equal to the area of the clamping
adaptions to eliminate edge leakage. Gaskets should be used with caution
because in some cases, and with repeated-use gaskets may deform mechanism. Label to maintain specimen identity.
resulting in a small change in test area.Aweighted ring can be used with
fabrics, such as knits or those that readily conform to the test head. The
weighted ring is not recommended for lofty or stiff fabric. TABLE 1 Number of Rolls or Pieces of Fabric in the Lot Sample
Number of Rolls or Pieces in Number of Rolls or Pieces
6.1.3 Means for drawing a steady flow of air perpendicu-
Lot, Inclusive in Lot Sample
larly through the test area and for adjusting the airflow rate that
1to3 all
4to24 4
For additional information on obtaining apparatus, equipment, or supplies that
25 to 50 5
may be suitable for use in this standard, please visit the ASTM Manufacturers’ over 50 10 % to a maximum of 10 rolls or pieces
Equipment Directory at www.astm.org.
´2
D737–04 (2008)
7.3.1.1 Take specimens or position test areas representing a 10.6 Remove the tested specimen and continue as directed
broaddistributionacrossthelengthandwidth,preferablyalong in 10.3-10.5 until ten specimens have been tested for each
the diagonal of the laboratory sample, and no nearer the edge laboratory sampling unit.
than one tenth its width unless otherwise agreed upon between 10.6.1 When a 95 % confidence level for results has been
the purchaser and supplier. Ensure specimens are free of folds, agreed upon in a material specification or contract order, fewer
creases, or wrinkles. Avoid getting oil, water, grease, and so test specimens may be sufficient. In any event, the number of
forth, on the specimens when handling. tests should be at least four.
8. Preparation of Test Apparatus and Calibration
11. Calculation
8.1 Set-up procedures for machines from different manufac-
11.1 Air Permeability, Individual Specimens—Calculate the
turers may vary. Prepare and verify calibration of the air
air permeability of individual specimens using values read
permeability tester as directed in the manufacturer’s instruc- 3 2
directlyfromthetestinstrumentinSIunitsascm /s/cm andin
3 2
tions.
inch-pound units as ft /min/ft , rounded to three significant
8.2 When using microprocessor automatic data gathering
digits. When calculating air permeability results, follow the
systems, set the appropriate parameters as specified in the
manufacturer’s instructions as applicable.
manufacturer’s instructions.
NOTE 4—For air permeability results obtained 600 m (2000 ft) above
8.3 For best results, level the test instrument.
sea level, correction factors may be required.
8.4 Verify calibration for the range and required water
pressure differential that is expected for the material to be 11.2 Air Permeability, Average—Calculate the average air
permeability for each laboratory sampling unit and for the lot.
tested.
11.3 Standard Deviation, Coeffıcient of Variation—
9. Conditioning
Calculate when requested.
9.1 Precondition the specimens by bringing them to ap- 11.4 Computer-Processed Data—When data are automati-
proximate moisture equilibrium in the standard atmosphere for cally computer-processed, calculations are generally contained
preconditioning textiles as specified in Practice D1776. in the associated software. It is recommended that computer-
9.2 After preconditioning, bring the test specimens to mois- processed data be verified against known property values and
ture equilibrium for testing in the standard atmosphere for its software described in the report.
testing textiles as specified in Practice D1776 or, if applicable,
in the specified atmosphere in which the testing is to be 12. Report
performed.
12.1 Report that the air permeability was determined in
9.3 When it is known that the material to be tested is not
accordance with Test Method D737. Describe the material or
affected by heat or moisture, preconditioning and conditioning
product sampled and the method of sampling used.
is not required when agreed upon in a material specification or
12.2 Report the following information for each laboratory
contract order.
sampling unit and for the lot as applicable to a material
specification or contract order:
10. Procedure
12.2.1 Air permeability.
10.1 Test the conditioned specimens in the standard atmo-
12.2.2 When calculated, the standard deviation or the coef-
sphere for testing textiles, which is 21 6 1°C (70 6 2°F) and
ficient of variation.
65 6 2 % relative humidity, unless otherwise specified in a
12.2.3 Pressure differential between the fabric surfaces.
material specification or contract order.
12.2.4 For computer-processed data, identify the program
10.2 Handle the test specimens carefully to avoid altering
(software) used.
the natural state of the material.
12.2.5 Manufacturer and model of test instrument.
10.3 Place each test specimen onto the test head of the test
12.2.6 Any modification of this test method or equipment
instrument, and perform the test as specified in the manufac-
inclu
...
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