ASTM D737-04(2008)e1
(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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NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
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´1
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.
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/D0737-04R08E01.
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.
3 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.
´1
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.Suchyarnextensionwouldopenupthefabric, 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.
´1
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-
including changing or adding gaskets.
turer’s operating instructions.
10.3.1 Place coated test specimens wit
...
This document is not anASTM standard and is intended only to provide the user of anASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
´1
Designation:D737–96 Designation:D737–04 (Reapproved 2008)
Standard Test Method for
Air Permeability of Textile Fabrics
This standard is issued under the fixed designation D 737; 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.
1. 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.
2. Referenced Documents
2.1 ASTM Standards:
D 123 Terminology Relating to Textiles
D 1776Practice for Conditioning Textiles for Testing Practice for Conditioning and Testing Textiles
D 2904 Practice for Interlaboratory Testing of a Textile Test Method Thatthat Produces Normally Distributed Data
D 2906Practice for Statements on Precision and Bias for Textiles Practice for Statements on Precision and Bias for Textiles
D 4850 Terminology Relating to Fabric
F 778Methods for Gas Flow Resistance Testing of Filtration Media
2.2ASTM Adjuncts:
TEX-PAC
NOTE1—TEX-PAC is a group of programs on floppy disks available through ASTM Headquarters, 100 Barr Harbor Drive, West Conshohocken, PA
19428. Methods for Gas Flow Resistance Testing of Filtration Media
3. Terminology
3.1Definitions—For definitions of other textile terms used in this test method refer to Terminology D123
3.1 For definition of textile terms used in this test method: air permeability, and fabric, refer to Terminology D 4850.
3.2Definitions of Terms Specific to This Standard:
3.2.1air permeability, n—the rate of air flow passing perpendicularly through a known area under a prescribed air pressure
differential between the two surfaces of a material.
3.2.1.1Discussion—Air permeability of fabric at a stated pressure differential between two surfaces of the fabric is generally
3 2 3 2
expressed in SI units as cm /s/cm and in inch-pound units as or ft /min/ft calculated at operating conditions.
3.2.2cross-machine direction, CD, n—the direction in the plane of the fabric perpendicular to the direction of manufacture.
3.2.2.1Discussion—This term is used to refer to the direction analogous to coursewise or filling direction in knitted or woven
fabrics, respectively.
3.2.3fabric, in textiles, n—a planar structure consisting of yarns or fibers.
3.2.4machine direction, MD, n—the direction in the plane of the fabric parallel to the direction of manufacture.
This test method is under the jurisdiction ofASTM Committee D13 onTextiles and is the direct responsibility of Subcommittee D13.59 on FabricTest Methods, General.
Current edition approved Feb. 10, 1996. Published April 1996. Originally published as D737–43T. Discontinued November 1995 and reinstated as D737–96.
Current edition approved July 1, 2008. Published August 2008. Originally approved in 1943 . Last previous edition approved in 2004 as D 737 – 04.
For referencedASTM standards, visit theASTM website, www.astm.org, or contactASTM Customer Service at service@astm.org. For Annual Book of ASTM Standards
, Vol 07.01.volume information, refer to the standard’s Document Summary page on the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
´1
D737–04 (2008)
3.2.4.1Discussion—This term is used to refer to the direction analogous to warpwise or warp direction in knitted or woven
fabrics, respectively.
3.2 For definitions of cross-machine direction; machine direction and other textile terms used in this test method, refer to
Terminology D 123.
4. Summary of Test Method
4.1 The rate of air flow passing perpendicularly through a known area of fabric is adjusted to obtain a prescribed air pressure
differential between the two fabric surfaces. From this rate of air flow, the air permeability of the fabric is determined.
5. Significance and Use
5.1 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.
5.1.1In case of a dispute arising from differences in reported test results when using this test method for acceptance testing of
commercial shipments, the purchaser and the supplier should conduct comparative tests to determine if there is a statistical bias
between their laboratories. Competent statistical assistance is recommended for the investigation of bias.As a minimum, the two
parties should take a group of test specimens that are as homogeneous as possible and that are from a lot of material of the type
in question. Test specimens then should be randomly assigned in equal numbers to each laboratory for testing. The average results
from the two laboratories should be compared using the appropriate statistical analysis and an acceptable probability level chosen
by the two parties before testing is begun. If a bias is found, either its cause must be found and corrected, or the purchaser and
the supplier must agree to interpret future test results with consideration of the known bias.
5.1.1 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,ensurethetestsamplestobeusedareashomogeneousaspossible,aredrawnfromthematerialfromwhichthedisparate
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.
5.2 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
toairpermeability.Airpermeabilityalsocanbeusedtoprovideanindicationofthebreathabilityofweather-resistantandrainproof
fabrics, or of coated fabrics in general, and to detect changes during the manufacturing process.
5.3 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.
5.4 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 with different surface textures on either side can have a different air permeability depending upon the
direction of air flow.
5.4.1 For woven fabric, yarn twist also is important. As twist increases, the circularity and density of the yarn increases, thus
reducing the yarn diameter and the cover factor and increasing the air permeability.Yarn crimp and weave influence the shape and
areaoftheintersticesbetweenyarnsandmaypermityarnstoextendeasily.Suchyarnextensionwouldopenupthefabric,increase
the free area, and increase the air permeability.
5.4.2 Increasingyarntwistalsomayallowthemorecircular,high-densityyarnstobepackedcloselytogetherinatightlywoven
structure with reduced air permeability. For example, a worsted gabardine fabric may have lower air permeability than a woolen
hopsacking fabric.
6. Apparatus
6.1 Air Permeability Testing Apparatus consisting of the following:
2 2
6.1.1 Test Head that provides a circular test area of 38.3 cm (5.93 in. )6 0.3 %.
2 2 2 2 2 2
NOTE 21—Alternate test areas may be used, such as 5 cm (0.75 in. ), 6.45 cm (1.0 in. ), and 100 cm (15.5 in. ).
6.1.2 Clamping System to Secure Test Specimens, of different thicknesses under a force of at least 50 65N(11 6 1 lbf) to the
test head without distortion and minimal edge leakage underneath the test specimen.
6.1.2.1 A suitable means to minimize edge leakage is to use 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 specimen.
Annual Book of ASTM Standards, Vol 14.02.
:Foradditionalinformationonobtainingapparatus,equipment,orsuppliesthatmaybesuitableforuseinthisstandard,pleasevisittheASTMManufacturers’Equipment
Directory at www.astm.org.
´1
D737–04 (2008)
NOTE3—Since 2—Since air leakage may affect test results, precautions must be taken, especially with very heavy or lofty fabrics, to prevent leakage.
The use of a weighted ring and rubber gaskets on the clamp surfaces has been found to be helpful.Test MethodMethods F 778 describes a series of usable
clamping adaptions to eliminate edge leakage. Gaskets should be used with caution because in some cases, and with repeated-use gaskets may deform
resultinginasmallchangeintestarea.Aweightedringcanbeusedwithfabrics,suchasknitsorthosethatreadilyconformtothetesthead.Theweighted
ring is not recommended for lofty or stiff fabric.
6.1.3 Means for drawing a steady flow of air perpendicularly through the test area and for adjusting the airflow rate that
preferably provides pressure differentials of between 100 and 2500 Pa (10 and 250 mm or 0.4 and 10 in. of water) between the
two surfaces of the fabric being tested.At a minimum, the test apparatus must provide a pressure drop of 125 Pa (12.7 mm or 0.5
in. of water) across the specimen.
6.1.4 Pressure Gage or Manometer,connectedtothetestheadunderneaththetestspecimentomeasurethepressuredropacross
the test specimen in pascals (millimetres or inches) of water with an accuracy of 62%.
3 2
6.1.5 Flowmeter, volumetric counter or measuring aperture to measure air velocity through the test area in cm /s/cm
3 2
(ft /min/ft ) with an accuracy of 62%.
6.1.6 Calibration Plate, or other means, with a known air permeability at the prescribed test pressure differential to verify the
apparatus.
6.1.7 Means of calculating and displaying the required results, such as scales, digital display, and computer-driven systems.
6.2 Cutting Dies or Templates, to cut specimens having dimensions at least equal to the area of the clamping surfaces of the
test apparatus (optional).
7. Sampling and Test Specimens
7.1 Lot Sample—As a lot sample for acceptance testing, randomly select the number of rolls or pieces of fabric directed in an
applicable material specification or other agreement between the purchaser and the supplier. Consider the rolls or pieces of fabric
to be the primary sampling units. In the absence of such an agreement, take the number of fabric rolls or pieces specified in Table
1.
NOTE4—An 3—An adequate specification or other agreement between the purchaser and the supplier requires taking into account the variability
between rolls or pieces of fabric and between specimens from a swatch from a roll or piece of fabric to provide a sampling plan with a meaningful
producer’s risk, consumer’s risk, acceptable quality level, and limiting quality level.
7.2 Laboratory Sample—For acceptance testing, take a swatch extending the width of the fabric and approximately1m(1yd)
along the lengthwise direction from each roll or piece in the lot sample. For rolls of fabric, take a sample that will exclude fabric
from the outer wrap of the roll or the inner wrap around the core of the roll of fabric.
7.3 Test Specimens—From each laboratory sampling unit, take ten specimens unless otherwise agreed upon between purchaser
and supplier. Use the cutting die or template described in 6.2, or if practical, make air permeability tests of a textile fabric without
cutting.
7.3.1 Cutting Test Specimens—When cutting specimens, cut having dimensions at least equal to the area of the clamping
mechanism. Label to maintain specimen identity.
7.3.1.1 Take specimens or position test areas representing a broad distribution across the length and width, preferably along the
diagonal of the laboratory sample, and no nearer the edge than one tenth its width unless otherwise agreed upon between the
purchaser and supplier. Ensure specimens are free of folds, creases, or wrinkles.Avoid getting oil, water, grease, and so forth, on
the specimens when handling.
8. Preparation of Test Apparatus and Calibration
8.1 Set-up procedures for machines from different manufacturers may vary. Prepare and verify calibration of the air
permeability tester as directed in the manufacturer’s instructions.
8.2 When using microprocessor automatic data gathering systems, set the appropriate parameters as specified in the
manufacturer’s instructions.
8.3 For best results, level the test instrument.
8.4 Verify calibration for the range and required water pressure differential that is expected for the material to be tested.
9. Conditioning
9.1 Precondition the specimens by bringing them to approximate moisture equilibrium in the standard atmosphere for
preconditioning textiles as specified in Practice D 1776.
TABLE 1 Number of Rolls or Pieces of Fabric in the Lot Sample
Number of Rolls or Pieces in Number of Rolls or Pieces
Lot, Inclusive in Lot Sample
1to3 all
4to24 4
25 to 50 5
over 50 10 % to a maximum of 10 rolls or pieces
´1
D737–04 (2008)
9.2 After preconditioning, bring the test specimens to moisture equilibrium
...
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