ASTM D737-18(2023)

This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: D737 − 18 (Reapproved 2023)
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 U.S. Department of Defense.
1. Scope Method that Produces Normally Distributed Data (With-
drawn 2008)
1.1 This test method covers the measurement of the air
D2906 Practice for Statements on Precision and Bias for
permeability of textile fabrics.
Textiles (Withdrawn 2008)
1.2 This test method applies to most fabrics including
D4850 Terminology Relating to Fabrics and Fabric Test
woven fabrics, nonwoven fabrics, air bag fabrics, blankets,
Methods
napped fabrics, knitted fabrics, layered fabrics, and pile fabrics.
F778 Methods for Gas Flow Resistance Testing of Filtration
The fabrics may be untreated, heavily sized, coated, resin-
Media
treated, or otherwise treated.
3. Terminology
1.3 The values stated in SI units are to be regarded as the
standard. The values stated in inch-pound units may be 3.1 For definition of textile terms used in this test method:
approximate. air permeability, and fabric, refer to Terminology D4850.
1.4 This standard does not purport to address all of the
3.2 For definitions of cross-machine direction; machine
safety concerns, if any, associated with its use. It is the
direction and other textile terms used in this test method, refer
responsibility of the user of this standard to establish appro-
to Terminology D123.
priate safety, health, and environmental practices and deter-
4. Summary of Test Method
mine the applicability of regulatory limitations prior to use.
1.5 This international standard was developed in accor-
4.1 The rate of air flow passing perpendicularly through a
dance with internationally recognized principles on standard-
known area of fabric is adjusted to obtain a prescribed air
ization established in the Decision on Principles for the
pressure differential between the two fabric surfaces. From this
Development of International Standards, Guides and Recom-
rate of air flow, the air permeability of the fabric is determined.
mendations issued by the World Trade Organization Technical
5. Significance and Use
Barriers to Trade (TBT) Committee.
5.1 This test method is considered satisfactory for accep-
2. Referenced Documents
tance testing of commercial shipments since current estimates
of between-laboratory precision are acceptable, and this test
2.1 ASTM Standards:
method is used extensively in the trade for acceptance testing.
D123 Terminology Relating to Textiles
5.1.1 If there are differences of practical significance be-
D1776/D1776M Practice for Conditioning and Testing Tex-
tween reported test results for two laboratories (or more),
tiles
comparative tests should be performed to determine if there is
D2904 Practice for Interlaboratory Testing of a Textile Test
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
This test method is under the jurisdiction of ASTM Committee D13 on Textiles
and is the direct responsibility of Subcommittee D13.59 on Fabric Physical Test
from which the disparate test results were obtained, and are
Methods A.
randomly assigned in equal number to each laboratory for
Current edition approved June 1, 2023. Published June 2023. Originally
testing. The test results from the two laboratories should be
approved in 1943. Last previous edition approved in 2018 as D737 – 18. DOI:
10.1520/D0737-18R23. compared using a statistical test for unpaired data, at a
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
Standards volume information, refer to the standard’s Document Summary page on The last approved version of this historical standard is referenced on
the ASTM website. www.astm.org.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D737 − 18 (2023)
NOTE 2—Since air leakage may affect test results, precautions must be
probability level chosen prior to the testing series. If bias is
taken, especially with very heavy or lofty fabrics, to prevent leakage. The
found, either its cause must be found and corrected, or future
use of a weighted ring and rubber gaskets on the clamp surfaces has been
test results for that material must be adjusted in consideration
found to be helpful. Methods F778 describes a series of usable clamping
of the known bias.
adaptions to eliminate edge leakage. Gaskets should be used with caution
because in some cases, and with repeated-use gaskets may deform
5.2 Air permeability is an important factor in the perfor-
resulting in a small change in test area. A weighted ring can be used with
mance of such textile materials as gas filters, fabrics for air
fabrics, such as knits or those that readily conform to the test head. The
bags, clothing, mosquito netting, parachutes, sails, tentage, and
weighted ring is not recommended for lofty or stiff fabric.
vacuum cleaners. In filtration, for example, efficiency is
6.1.3 Means for drawing a steady flow of air perpendicu-
directly related to air permeability. Air permeability also can be
larly through the test area and for adjusting the airflow rate that
used to provide an indication of the breathability of weather-
preferably provides pressure differentials of between 100 Pa
resistant and rainproof fabrics, or of coated fabrics in general,
and 2500 Pa (10 mm and 250 mm or 0.4 in. and 10 in. of water)
and to detect changes during the manufacturing process.
between the two surfaces of the fabric being tested. At a
5.3 Performance specifications, both industrial and military,
minimum, the test apparatus must provide a pressure drop of
have been prepared on the basis of air permeability and are
125 Pa (12.7 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.
head underneath the test specimen to measure the pressure drop
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 %.
an appreciable effect upon air permeability by causing a change
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
permeability at the prescribed test pressure differential to verify
direction of air flow.
the apparatus.
5.4.1 For woven fabric, yarn twist also is important. As twist
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
to extend easily. Such yarn extension would open up the fabric,
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 Increasing yarn twist also may allow the more circular,
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 Head that provides a circular test area of 38.3 cm
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. ),
2 from a roll or piece of fabric to provide a sampling plan with a meaningful
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 6 5 N (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 A suitable 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)
clamping ring 20 mm (0.75 in.) wide and 3 mm (0.125 in.)
thick around the test area above and underneath the test
TABLE 1 Number of Rolls or Pieces of Fabric in the Lot Sample
specimen.
Number of Rolls or Pieces in Number of Rolls or Pieces
Lot, Inclusive in Lot Sample
1 to 3 all
4 to 24 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 − 18 (2023)
exclude fabric from the outer wrap of the roll or the inner wrap 10.2 Handle the test specimens carefully to avoid altering
around the core of the roll of fabric. the natural state of the material.
7.3 Test Specimens—From each laboratory sampling unit, 10.3 Place each test specimen onto the test head of the test
take ten specimens unless otherwise agreed upon between instrument, and perform the test as specified in the manufac-
purchaser and supplier. Use the cutting die or template de- turer’s operating instructions.
scribed in 6.2, or if practical, make air permeability tests of a 10.3.1 Place coated test specimens with the coated side
textile fabric without cutting. down (towards low pressure side) to minimize edge leakage.
7.3.1 Cutting Test Specimens—When cutting specimens, cut
10.4 Make tests at the water pressure differential specified
having dimensions at least equal to the area of the clamping
in a material specification or contract order. In the absence of
mechanism. Label to maintain specimen identity.
a material specification or contract order, use a water pressure
7.3.1.1 Take specimens or position test areas representing a
differential of 125 Pa (12.7 mm or 0.5 in. of water).
broad distributi
...