ISO 9237 Unveiled: A Comprehensive Guide to Textile Air Permeability Testing

ISO 9237:1995 Textiles—Determination of the permeability of fabrics to air is an international standard formulated by the ISO/TC 38 Textile Technical Committee, first published in 1995 and confirmed as current in 2023. It serves as a cornerstone for standardizing the measurement of fabric air permeability, ensuring consistency and comparability of test results worldwide, and supporting textile R&D, quality control, and international trade. This article elaborates on its core content, testing procedures, application values, and more.

I. Core Definitions and Scope

1. Core Definition: Air permeability refers to the velocity of air flowing perpendicularly through a test specimen under specified conditions of test area, pressure difference, and time, commonly expressed in units such as L/(m²·s) or mm/s, reflecting a fabric’s ability to conduct air.
2. Scope of Application: Applicable to most fabric types, including woven, knitted, non-woven fabrics, industrial technical fabrics, and various air-permeable textile products. It is not suitable for special materials with high bulkiness, easy compressibility, or extremely low air permeability (nearly airtight), and additional verification of test conditions is required for such materials.
3. Key Test Parameters

Parameter	Standard Value	Notes
Test Pressure Difference	100Pa (General)	Adjustable according to materials, ranging from 0 to 5000Pa
Test Area	20cm² (Preferred)	5cm², 50cm², 100cm² are optional
Environmental Conditions	Temperature (20±2)℃, Relative Humidity (65±4)%	Specimens shall be conditioned in this environment for at least 24h before testing
Measurement Accuracy	≤±2%	Ensure data repeatability

II. Testing Principle and Complete Procedures

1). Testing Principle: The “constant pressure-flow measurement” method is adopted. A specified pressure difference is applied on both sides of the specimen, the volume flow rate of air passing vertically through the specimen of a fixed area is measured, and the air permeability per unit area is calculated. The formula is R = qᵥ/A×167, where R is the air permeability in mm/s, qᵥ is the average flow rate, and A is the test area.
2). Detailed Testing Procedures
1.Sample Preparation: Cut at least 10 specimens from different parts of the sample, avoiding wrinkles and defects. Condition the specimens in the standard temperature and humidity environment for more than 24h before testing.
2.Clamping and Sealing: Clamp the specimen flat on the test head without distortion or air leakage to prevent edge air leakage from affecting the data.
3.Parameter Setting: Select the test area (e.g., 20cm²) and pressure difference (e.g., 100Pa), and start the instrument to stabilize the air flow.
4.Data Collection: Record the flow data of each group, repeat the test 3-5 times for each specimen, and take the average value.
5.Result Calculation: Calculate the arithmetic mean, coefficient of variation, mark the 95% confidence interval, and convert the air permeability unit according to the formula.
6.Instrument Calibration: Perform zero-point calibration when starting the machine every day, and verify the accuracy with a standard film regularly to ensure that the error is ≤±2%.

III. Application Scenarios and Industrial Value

1. Quality Control: Textile mills monitor production consistency through testing. For example, sportswear fabrics require high air permeability (usually 900L/(m²·s)), and medical protective fabrics need low air permeability (about 10L/(m²·s)) to block pathogens.
2. Product R&D: Guide the development of new materials. For instance, outdoor equipment needs to balance air permeability and wind resistance, and filter materials need to match a specific air permeability to balance efficiency and resistance.
3. International Trade: The unified test standard eliminates technical barriers. For example, Asian factories and European buyers conduct tests in accordance with ISO 9237, and the results are mutually recognized, reducing the risk of trade disputes.
4. Cross-field Extension: In addition to textiles, fields such as automotive filter materials, geotextiles, and medical non-woven fabrics also refer to this standard to evaluate air permeability performance.

IV. Common Problems and Precautions

1. Sources of Error: Uneven clamping of specimens, edge air leakage, fluctuations in ambient temperature and humidity, and uncalibrated instruments can all lead to data deviations.
2. Handling of Special Materials: For highly elastic fabrics, the clamping force should be controlled to prevent deformation. For highly air-permeable materials, a small test area can be selected, and for low air-permeable materials, the pressure difference can be increased or the test area can be expanded.
3. Result Interpretation: Higher air permeability is not necessarily better. It should be judged according to the product application. For example, winter coats need a moderate air permeability to balance warmth and comfort.

V. Comparison with Relevant Standards

ISO 9237, ASTM D737 (American standard for fabric air permeability), and GB/T 5453 (Chinese national standard equivalent to ISO 9237) have the same core principle. The differences mainly lie in the optional range of test parameters, data accuracy requirements, and report format. ISO 9237 is preferred in international trade to ensure global versatility.

Conclusion

As the core international standard for textile air permeability testing, ISO 9237 provides a unified technical basis for the industry. Mastering its test specifications, parameter control, and result application is of great significance for improving product quality and promoting international circulation. Laboratories and enterprises should strictly follow the standard procedures to ensure the accuracy and reliability of test data.

Our product GA-4004 Fabric Air Permeability Tester meets this standard.

GA-4004 Fabric Air Permeability Tester

Standards
GB/T 5453、GB/T 13764、ISO 9237、ISO 7231、ISO 5636、BS 5636、ASTM D737
DIN 53887、JIS L1096

Uses
For a variety of textile fabrics, including industrial fabrics, non-woven fabrics and other textile
products and other breathable material permeability measurement.

Instrument characteristics
1, imported high-precision pressure and differential pressure sensor to ensure data accuracy.
2, microcomputer processing, test results displayed directly, without artificial look-up table calculations.
3, built-in 7 kinds of test units mm / s, m3/m2.min, cm3/cm2.s, m3/m2.h, cfm, L/dm2.min, L/m2.s test unit can switch according to demand.
4, touch screen control, two-way selection menu operation in English, available on-line operation.

Specifications
1, the sample pressure range: 1 ~ 4000Pa
2, the air permeability can be measured: 0.1 ~ 12000mm / s
3, the measurement error: ≤ ± 2%
4, can be measured fabric thickness: ≤ 12mm
5, the test area: 5cm2; 20cm2; 50cm2; 100cm2
Ф50mm (≈ 19.6cm2) Ф70mm (≈ 38.5cm2)
6, the nozzle parameters:

7, Power: AC220V 50Hz 2KW
8 Shape: 1070 × 670 × 1080mm
9, Weight: 75Kg

Product link:

https://www.gonoava.com/product/ga-4004-fabric-air-permeability-tester/

Contact:

Email: arlenliu@gonoava.com
WhatsApp: 0086 18670728798(We chat)
If you have any questions you can send me a message or email.