ASTM D737-04(2012)
(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.
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Standards Content (Sample)
NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
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Designation: D737 − 04(Reapproved 2012)
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.
1. Scope 3. Terminology
1.1 This test method covers the measurement of the air
3.1 For definition of textile terms used in this test method:
permeability of textile fabrics.
air permeability, and fabric, refer to Terminology D4850.
1.2 This test method applies to most fabrics including
3.2 For definitions of cross-machine direction; machine
woven fabrics, nonwoven fabrics, air bag fabrics, blankets,
direction and other textile terms used in this test method, refer
nappedfabrics,knittedfabrics,layeredfabrics,andpilefabrics.
to Terminology D123.
The fabrics may be untreated, heavily sized, coated, resin-
treated, or otherwise treated.
4. Summary of Test Method
1.3 The values stated in SI units are to be regarded as the
4.1 The rate of air flow passing perpendicularly through a
standard. The values stated in inch-pound units may be
known area of fabric is adjusted to obtain a prescribed air
approximate.
pressure differential between the two fabric surfaces. From this
1.4 This standard does not purport to address all of the
rate of air flow, the air permeability of the fabric is determined.
safety concerns, if any, associated with its use. It is the
responsibility of the user of this standard to establish appro-
5. Significance and Use
priate safety and health practices and determine the applica-
bility of regulatory limitations prior to use. 5.1 This test method is considered satisfactory for accep-
tance testing of commercial shipments since current estimates
2. Referenced Documents
of between-laboratory precision are acceptable, and this test
method is used extensively in the trade for acceptance testing.
2.1 ASTM Standards:
D123 Terminology Relating to Textiles 5.1.1 If there are differences of practical significance be-
D1776 Practice for Conditioning and Testing Textiles tween reported test results for two laboratories (or more),
D2904 Practice for Interlaboratory Testing of a Textile Test comparative tests should be performed to determine if there is
Method that Produces Normally Distributed Data (With- a statistical bias between them, using competent statistical
drawn 2008) assistance. As a minimum, ensure the test samples to be used
D2906 Practice for Statements on Precision and Bias for are as homogeneous as possible, are drawn from the material
Textiles (Withdrawn 2008) from which the disparate test results were obtained, and are
D4850 Terminology Relating to Fabrics and Fabric Test randomly assigned in equal number to each laboratory for
Methods testing. The test results from the two laboratories should be
compared using a statistical test for unpaired data, at a
F778 Methods for Gas Flow Resistance Testing of Filtration
Media 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
This test method is under the jurisdiction ofASTM Committee D13 on Textiles
of the known bias.
and is the direct responsibility of Subcommittee D13.59 on Fabric Test Methods,
General.
5.2 Air permeability is an important factor in the perfor-
Current edition approved July 1, 2012. Published August 2012. Originally
mance of such textile materials as gas filters, fabrics for air
approved in 1943 . Last previous edition approved in 2008 as D737 – 04(2008).
bags, clothing, mosquito netting, parachutes, sails, tentage, and
DOI: 10.1520/D0737-04R12.
vacuum cleaners. In filtration, for example, efficiency is
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
directlyrelatedtoairpermeability.Airpermeabilityalsocanbe
Standards volume information, refer to the standard’s Document Summary page on
used to provide an indication of the breathability of weather-
the ASTM website.
resistant and rainproof fabrics, or of coated fabrics in general,
The last approved version of this historical standard is referenced on
www.astm.org. and to detect changes during the manufacturing process.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D737 − 04 (2012)
5.3 Performance specifications, both industrial and military, test apparatus must provide a pressure drop of 125 Pa (12.7
have been prepared on the basis of air permeability and are mm or 0.5 in. of water) across the specimen.
used in the purchase of fabrics where permeability is of 6.1.4 Pressure Gage or Manometer, connected to the test
interest. headunderneaththetestspecimentomeasurethepressuredrop
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
in the length of airflow paths through a fabric. Hot calendaring
3 2
to measure air velocity through the test area in cm /s/cm
can be used to flatten fabric components, thus reducing air
3 2
(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
and area of the interstices between yarns and may permit yarns 6.2 Cutting Dies or Templates, to cut specimens having
toextendeasily.Suchyarnextensionwouldopenupthefabric, dimensions at least equal to the area of the clamping surfaces
increase the free area, and increase the air permeability. of the test apparatus (optional).
5.4.2 Increasingyarntwistalsomayallowthemorecircular,
7. Sampling and Test Specimens
high-density yarns to be packed closely together in a tightly
woven structure with reduced air permeability. For example, a
7.1 Lot Sample—As a lot sample for acceptance testing,
worsted gabardine fabric may have lower air permeability than
randomly select the number of rolls or pieces of fabric directed
a woolen hopsacking fabric.
in an applicable material specification or other agreement
between the purchaser and the supplier. Consider the rolls or
6. Apparatus
pieces of fabric to be the primary sampling units. In the
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:
6.1.1 Test Headthatprovidesacirculartestareaof38.3cm
NOTE 3—An adequate specification or other agreement between the
(5.93 in. )6 0.3 %.
purchaser and the supplier requires taking into account the variability
between rolls or pieces of fabric and between specimens from a swatch
2 2
NOTE 1—Alternate test areas may be used, such as 5 cm (0.75 in. ),
fromarollorpieceoffabrictoprovideasamplingplanwithameaningful
2 2 2 2
6.45 cm (1.0 in. ), and 100 cm (15.5 in. ).
producer’s risk, consumer’s risk, acceptable quality level, and limiting
quality level.
6.1.2 Clamping System to Secure Test Specimens, of differ-
ent thicknesses under a force of at least 50 65N(11 6 1 lbf)
7.2 Laboratory Sample—For acceptance testing, take a
to the test head without distortion and minimal edge leakage
swatch extending the width of the fabric and approximately 1
underneath the test specimen.
m (1 yd) along the lengthwise direction from each roll or piece
6.1.2.1 Asuitable means to minimize edge leakage is to use
in the lot sample. For rolls of fabric, take a sample that will
a 55 Type A durometer hardness polychloroprene (neoprene)
exclude fabric from the outer wrap of the roll or the inner wrap
clamping ring 20 mm (0.75 in.) wide and 3 mm (0.125 in.)
around the core of the roll of fabric.
thick around the test area above and underneath the test
7.3 Test Specimens—From each laboratory sampling unit,
specimen.
take ten specimens unless otherwise agreed upon between
NOTE 2—Since air leakage may affect test results, precautions must be
purchaser and supplier. Use the cutting die or template de-
taken, especially with very heavy or lofty fabrics, to prevent leakage. The
scribed in 6.2, or if practical, make air permeability tests of a
use of a weighted ring and rubber gaskets on the clamp surfaces has been
textile fabric without cutting.
found to be helpful. Methods F778 describes a series of usable clamping
7.3.1 Cutting Test Specimens—When cutting specimens, cut
adaptions to eliminate edge leakage. Gaskets should be used with caution
because in some cases, and with repeated-use gaskets may deform having dimensions at least equal to the area of the clamping
resulting in a small change in test area.Aweighted ring can be used with
mechanism. Label to maintain specimen identity.
fabrics, such as knits or those that readily conform to the test head. The
7.3.1.1 Take specimens or position test areas representing a
weighted ring is not recommended for lofty or stiff fabric.
broaddistributionacrossthelengthandwidth,preferablyalong
6.1.3 Means for drawing a steady flow of air perpendicu-
the diagonal of the laboratory sample, and no nearer the edge
larly through the test area and for adjusting the airflow rate that
preferably provides pressure differentials of between 100 and
TABLE 1 Number of Rolls or Pieces of Fabric in the Lot Sample
2500 Pa (10 and 250 mm or 0.4 and 10 in. of water) between
Number of Rolls or Pieces in Number of Rolls or Pieces
the two surfaces of the fabric being tested. At a minimum, the
Lot, Inclusive in Lot Sample
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.
D737 − 04 (2012)
than one tenth its width unless otherwise agreed upon between 10.6 Remove the tested specimen and continue as directed
the purchaser and supplier. Ensure specimens are free of folds, in 10.3-10.5 until ten specimens have been tested for each
creases, or wrinkles. Avoid getting oil, water, grease, and so laboratory sampling unit.
forth, on the specimens when handling. 10.6.1 When a 95 % confidence level for results has been
agreed upon in a material specification or contract order, fewer
8. Preparation of Test Apparatus and Calibration
test specimens may be sufficient. In any event, the number of
8.1 Set-up procedures for machines from different manufac-
tests should be at least four.
turers may vary. Prepare and verify calibration of the air
permeability tester as directed in the manufacturer’s instruc- 11. Calculation
tions.
11.1 Air Permeability, Individual Specimens—Calculate the
air permeability of individual specimens using values read
8.2 When using microprocessor automatic data gathering
3 2
directlyfromthetestinstrumentinSIunitsascm /s/cm andin
systems, set the appropriate parameters as specified in the
3 2
inch-pound units as ft /min/ft , rounded to three significant
manufacturer’s instructions.
digits. When calculating air permeability results, follow the
8.3 For best results, level the test instrument.
manufacturer’s instructions as applicable.
8.4 Verify calibration for the range and required water
NOTE 4—For air permeability results obtained 600 m (2000 ft) above
pressure differential that is expected for the material to be
sea level, correction factors may be required.
tested.
11.2 Air Permeability, Average—Calculate the average air
9. Conditioning
permeability for each laboratory sampling unit and for the lot.
9.1 Precondition the specimens by bringing them to ap-
11.3 Standard Deviation, Coeffıcient of Variation—
proximate moisture equilibrium in the standard atmosphere for
Calculate when requested.
preconditioning textiles as specified in Practice D1776.
11.4 Computer-Processed Data—When data are automati-
9.2 After preconditioning, bring the test specimens to mois-
cally computer-processed, calculations are generally contained
ture equilibrium for testing in the standard atmosphere for
in the associated software. It is recommended that computer-
testing textiles as specified in Practice D1776 or, if applicable,
processed data be verified against known property values and
in the specified atmosphere in which the testing is to be
its software described in the report.
performed.
12. Report
9.3 When it is known that the material to be tested is not
affected by heat or moisture, preconditioning and conditioning 12.1 Report that the air permeability was determined in
is not required when agreed upon in a material specification or
accordance with Test Method D737. Describe the material or
contract order.
product sampled and the method of sampling used.
12.2 Report the following information for each laboratory
10. Procedure
sampling unit and for the lot as applicable to a material
10.1 Test the conditioned specimens in the standard atmo-
specification or contract order:
sphere for testing textiles, which is 21 6 1°C (70 6 2°F) and
12.2.1 Air permeability.
65 6 2 % relative humidity, unless otherwise specified in a
12.2.2 When calculated, the standard deviation or the coef-
material specification or contract order.
ficient of variation.
10.2 Handle the test specimens carefully to avoid altering
12.2.3 Pressure differential between the fabric surfaces.
the natural state of the material.
12.2.4 For computer-processed data, identify the program
(software) used.
10.3 Place each test specimen onto the test head of the test
12.2.5 Manufacturer and model of test instrument.
instrument, and perform the test as specified in the manufac-
12.2.6 Any modification of this test method or equipment
turer’s operating instructions.
including changing or adding gaskets.
10.3.1 Place coated test specimens with the coated side
down (t
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