🔩 Textiles — air permeability of fabrics (woven, knitted, nonwovens, technical fabrics): rate of air flow through the test area of the specimen at a given pressure drop — recommended 20 cm2 and 100 Pa for apparel fabrics or 200 Pa for industrial fabrics, at least 10 measurements, result R in mm/s; PN-EN ISO 9237

Materials and NDT PN-EN ISO 9237

Overview

WHAT THE STANDARD COVERS. According to clause 1 of ISO 9237:1995 the standard describes a method for measuring the permeability of fabrics to air and is applicable to most types of fabrics, including industrial fabrics for technical purposes, nonwovens and made-up textile articles that are permeable to air. "Scope" field of the PKN card for PN-EN ISO 9237:1998 (Polish version): "A method for measuring air permeability is described, applicable to various types of products, including industrial products intended for technical applications and nonwovens capable of letting air through".

ACCORDING TO THE TEXT OF ISO 9237:1995 — TERMS, APPARATUS, PROCEDURE, CALCULATION (foreword, clauses 1–11). The standard was prepared by ISO/TC 38 (Textiles); first edition 1995-06-15; Annexes A and B are for information only. Normative references: ISO 48:1994 (rubber hardness), ISO 139:1973 (standard atmospheres for conditioning and testing of textiles), ISO 10012-1:1992 (metrological confirmation of measuring equipment). Definition (3.1): air permeability — velocity of an air flow passing perpendicularly through a test specimen under specified conditions of test area, pressure drop and time. Principle (clause 4): the rate of flow of air passing perpendicularly through a given area of fabric is measured at a given pressure difference across the fabric test area over a given time period. Sampling (clause 5): according to the material specification for the fabric or as agreed between the parties; in the absence of a specification — according to the example in Annex B. Atmospheres (clause 6): preconditioning, conditioning and testing — according to ISO 139. Apparatus (clause 7; metrological confirmation according to ISO 10012-1): circular specimen holder with an orifice for a test area of 5 cm2, 20 cm2, 50 cm2 or 100 cm2, with a tolerance on the test area not exceeding ± 0.5 % (adequate support of the specimen recommended for large areas); clamping of the specimen without distortion (air leakage at the edges shall be prevented — or the leakage measured separately and subtracted from the result); a guard ring device against leakage for optional use (Annex A.2.1); a pressure gauge indicating a pressure drop across the test area of 50 Pa, 100 Pa, 200 Pa or 500 Pa with an accuracy of at least 2 %; means for drawing a steady flow of air at controlled temperature and humidity through the holder and for adjusting the pressure drop between 50 Pa and 500 Pa; a flowmeter, volumetric counter or measuring aperture indicating the rate of air flow in dm3 (litres) per minute with an accuracy of at least ± 2 % (other units allowed at the same accuracy). Conditions (clause 8): samples are conditioned and tested in the standard atmosphere; recommended — test area 20 cm2, pressure drop 100 Pa for apparel fabrics and 200 Pa for industrial fabrics; where these pressure drops cannot be achieved or are not appropriate — 50 Pa or 500 Pa and/or a test area of 5, 50 or 100 cm2 if agreed between the parties; for comparison of results the same test area and the same pressure drop are recommended. Procedure (clause 9): the specimen is mounted in the holder with sufficient tension to eliminate wrinkles, without distorting it in its own plane, avoiding selvedges and areas with creases or folds; where the air permeability may differ between the two faces of the fabric, the face tested is stated; specimens coated on one side are clamped with the coating towards the lower pressure side; the suction fan is started and the air flow adjusted gradually to the required pressure drop; the air flow is recorded after at least 1 min or after steady conditions are achieved (some volumetric counters need an air flow volume of about 10 dm3 for the required accuracy); the test is repeated at different places of the sample at least 10 times under the same conditions. Calculation (clause 10): arithmetic mean of the readings and coefficient of variation (to the nearest 0.1 %) with the 95 % confidence interval; air permeability R in mm/s = qv / A × 167, where qv — mean rate of air flow in dm3/min (l/min), A — test area in cm2, 167 — conversion factor from dm3/min per cm2 to mm/s; for open fabrics and nonwovens R in m/s = qv / A × 0.167; the result R is rounded to 2 % of its value. Test report (clause 11): among others the test area in cm2, the pressure drop in Pa, the number of specimens, the atmospheres, the direction of air flow if required, deviations; result: mean R, coefficient of variation and 95 % confidence interval.

STATUS (PKN cards as of 10.11.2026). The card for PN-EN ISO 9237:1998 (Polish version) has no withdrawal label: published 10-12-1998, 9 pages, KT 26 for Textile Products, "Implements: EN ISO 9237:1995 [IDT], ISO 9237:1995 [IDT]", "Replaces: PN-P-04618:1989 - Polish version", ICS 59.080.30. The PKN search (query "PN-EN ISO 9237", 10.11.2026) shows only this card. iTeh catalogue (read 10.11.2026): ISO 9237:1995 — ISO/TC 38/SC 24, stage "9093 – International Standard confirmed" (confirmed in the periodic review); SIST EN ISO 9237:1999 — stage 6060.

HOW MANY LABORATORIES AND IN WHAT FORM (accreditation scope database of the service and the "Laboratories" tab on labcoda.pl, read 10.11.2026). The notation "PN-EN ISO 9237:1998" appears in 6 records at 5 Polish laboratories: AB 154, AB 198, AB 225 and AB 1421 with 1 record each, AB 164 — 2 records. Outside Poland — 6 records at 6 Czech laboratories (1001, 1004, 1224, 1401, 1591, 1730: "ČSN EN ISO 9237", in 1730 also "DIN EN ISO 9237", in 1001 next to ČSN EN 14683, příloha C). The "Laboratories" tab ("PN-EN ISO 9237") shows 11 laboratories (5 PL, 6 CZ) and 12 items. We have not compared the current PCA scope documents of these laboratories with the database.

WHAT THE LABORATORIES TEST (scope database, complete items — 6 Polish). AB 154, AB 164, AB 198 and AB 225 — flat textile products: air permeability. AB 1421 — flat textile products, woven and knitted fabrics: air permeability, range (0–10 000) mm/s.

WHERE AN APPARENTLY CORRECT RESULT IS EASY TO GET. Specimen: a measurement on the selvedge, at a crease or fold, a specimen mounted with wrinkles or stretched in its own plane are conditions other than in clause 9; air leakage at the edges overstates the flow — it has to be prevented or measured separately and subtracted. A fabric coated on one side is clamped with the coating towards the lower pressure side; with fabrics whose faces differ, the face tested has to be stated. Measurement: results are comparable only at the same test area and the same pressure drop — 100 Pa (apparel) and 200 Pa (industrial fabrics) are two different conditions; reading earlier than after 1 min or before the flow has stabilised. Calculation: R is calculated from the MEAN flow of at least 10 measurements, with the area in cm2 and the flow in dm3/min — the factor 167 gives mm/s, 0.167 gives m/s; mixing up the units changes the result a thousandfold. The coefficient of variation and the 95 % confidence interval are given with the result.

WHAT WE DO NOT GIVE. Parts read: the iTeh sample of ISO 9237:1995 (French version: foreword, clauses 1–8) and the iTeh sample of SIST EN ISO 9237:1999 (English version of ISO 9237:1995: foreword, clauses 1–11). We do not give the content of the informative Annexes A (checking calibration and conducting the test, guard ring A.2.1) and B (example of sampling) — we have not read them. We do not give the standard atmosphere conditions of ISO 139 or the requirements of ISO 10012-1 and ISO 48 — we have not read these standards. The standard gives no requirements for particular products (minimum or maximum air permeability) — they are given in product specifications.

Method principle

The specimen, clamped without wrinkles and distortion in a circular holder (area 5, 20, 50 or 100 cm2, ± 0.5 %), is subjected to a steady air flow up to the required pressure drop (recommended 20 cm2 and 100 Pa for apparel or 200 Pa for industrial fabrics; 50 or 500 Pa allowed); the flow rate (± 2 %) is read after at least 1 min, at least 10 times at different places, and the air permeability R = qv/A × 167 in mm/s (or × 0.167 in m/s) is given with the coefficient of variation and the 95 % confidence interval (ISO 9237:1995, clauses 7–10).

Applications

• Woven and knitted fabrics, nonwovens, industrial fabrics and made-up textile articles permeable to air (ISO 9237:1995, clause 1)
• Apparel fabrics (recommended pressure drop 100 Pa) and industrial fabrics (recommended pressure drop 200 Pa) — conditions from clause 8
• Replaced in PN the standard PN-P-04618:1989 (PKN card)
• In accreditation scopes: 5 Polish laboratories — flat textile products, woven and knitted fabrics; range up to 10 000 mm/s

Key parameters

Standard

Standard number

PN-EN ISO 9237:1998 (Polish version; implements EN ISO 9237:1995 and ISO 9237:1995 [IDT])

Title (PL)

Tekstylia — Wyznaczanie przepuszczalności powietrza wyrobów włókienniczych

Title (EN)

Textiles — Determination of the permeability of fabrics to air

Step-by-step procedure

1. Samples and conditioning

   Sampling according to the product specification or agreement (example — Annex B); conditioning and testing in the standard atmosphere according to ISO 139 (clauses 5, 6, 8).

2. Mounting

   Specimen in the holder with tension eliminating wrinkles, without distortion; no selvedges, creases or folds; tested face stated when the faces differ; coating towards the lower pressure side (clause 9).

3. Air flow

   Starting the suction fan and adjusting the flow gradually to the required pressure drop — recommended 100 Pa (apparel) or 200 Pa (industrial fabrics) at a test area of 20 cm2 (clauses 8–9).

4. Reading

   Flow rate after at least 1 min or after steady conditions; at least 10 measurements at different places under the same conditions (clause 9).

5. Calculation and test report

   Mean, coefficient of variation, 95 % confidence interval; R = qv/A × 167 (mm/s) or × 0.167 (m/s), rounded to 2 %; test area, pressure drop, number of specimens and atmospheres in the report (clauses 10–11). PN-EN ISO 9237:1998 — current (PKN card as of 10.11.2026).

Required equipment and apparatus

Health and safety (OHS)

• Suction fan and clamping specimen holder — care when mounting the specimen
• The part of the standard read gives no hazards of the test — NOT GIVEN
• TECHNICAL NOTE: results are compared only at the same test area and the same pressure drop

Frequently asked questions