Overview
ISO 9237:1995 specifies a laboratory method for determining the air permeability (permeability of fabrics to air) of most textiles, including woven and knitted fabrics, nonwovens, made-up textile articles and industrial/technical fabrics. The standard measures the flow rate of air passing perpendicularly through a defined fabric area under a specified pressure drop and time, then expresses results in standard units for comparison and quality control.
Key topics and requirements
- Scope and applicability: Applicable to most types of air‑permeable fabrics and textile articles. Annexes provide guidance on calibration and sampling.
- Test atmosphere and conditioning: Tests are to be performed after conditioning in standard atmospheres (see ISO 139 referenced in the standard).
- Apparatus:
- Circular specimen holder with orifices for standard test areas (examples: 5, 20, 50, 100 cm²) with ±0.5% tolerance.
- Clamping means to secure specimens without distortion; optional guard ring to prevent edge leakage.
- Pressure gauge/manometer capable of indicating pressure drops of typically 50, 100, 200 or 500 Pa (accuracy at least ±2%).
- Means to draw a steady, controlled airflow (suction fan) and a flowmeter/volumetric counter indicating flow in litres/min (accuracy at least ±2%).
- Metrological confirmation of equipment per ISO 10012‑1.
- Test conditions and procedure:
- Typical recommended pressure drops: 100 Pa for apparel fabrics, 200 Pa for industrial fabrics (50 Pa or 500 Pa may be used when appropriate).
- Record steady-state air flow after stability (≥1 minute or until steady).
- Repeat tests at multiple locations on the sample (recommendation: at least 10 readings under the same conditions).
- Calculation and reporting:
- Air permeability is calculated from the mean volumetric flow and test area using the conversion factor given in the standard (conversion from litres/min per cm² to mm/s); open fabrics may be expressed in m/s.
- Report the arithmetic mean, coefficient of variation, 95% confidence interval, test area, pressure drop, specimen count, conditioning atmosphere and any deviations.
Applications and users
ISO 9237 is used for:
- Quality control and specification verification in textile manufacturing (apparel, technical textiles, nonwovens).
- R&D and product development where breathability or air transfer is critical (sportswear, protective clothing, filtration media, automotive interiors, geotextiles).
- Acceptance testing between suppliers and buyers and regulatory or certification labs.
Typical users: textile testing laboratories, manufacturers, material engineers, product designers, procurement and QA teams.
Related standards
- ISO 139 - Standard atmospheres for conditioning and testing (referenced for conditioning).
- ISO 10012-1 - Metrological confirmation for measuring equipment.
- ISO 48 - Hardness test for rubber components used in clamps/gaskets (referenced quality).
Keywords: ISO 9237, air permeability, fabric permeability test, textiles, nonwovens, pressure drop, airflow through fabrics, textile testing.
