Insights and Experience on ISO 9237 Fabric Air Permeability Test

Air permeability is essential in the garment industry, especially in performance apparel, including sportswear. In this article, you will learn about air permeability and its importance and impact on garments. After completing this article, you can also perform an air permeability test according to ISO 9237.

What is the air permeability of fabric?

Air permeability is the property of a fabric to allow air to pass through it. Fabrics used in sportswear need maximum air to pass to maintain players’ body temperature for their performance, which requires high air permeability. It directly links with one’s comfort. On the other hand, low air permeability is also required in particular fields, including protective and safety clothing.

Air Permeability VS Breathability

Primarily, air permeability and breathability are considered the same features. But technically, both are relatively different. Breathability is the property of a material to the extent to which it releases warmth from the wearer’s body. Breathable clothing dissipates the heat and water vapors of the wearer’s body and prevents sweat buildup. This breathability is an essential requirement for athletic and sportswear. However, air permeability is how easily air can pass through a fabric. Breathability depends on fabric air permeability.

How to measure Air permeability

Different air permeability test methods are available to measure airflow. Following is a list for reference.

1. EN ISO 9237 – A method used to measure the air permeability of fabrics.
2. ASTM D737 – American Standard Test Method for Air Permeability of Textile Fabrics.
3. GB/T 5453 – A Chinese method for measuring the air permeability of fabrics.
4. JIS L 1096:2010 (test 8.26 Method C) – A Japanese method that deals with air permeability
5. BS 3424- part 16 – Determination of air permeability and testing of coated fabrics.
6. NWSP 70.1 – Measurement of the air permeability of nonwoven materials
7. BS EN ISO 9073-15 – This test method applies to most nonwovens, such as laminates, which are treated or untreated.

ISO 9237 vs ASTM D737

The most often used standards for determining fabric’s air permeability value are ASTM D737 and ISO 9237. However, they both have different sample preparation and conditioning requirements, measuring units, and different airflow ranges. These differences affect the air permeability test results, so you must choose the appropriate standard according to end-use. In this article, we learn about ISO 9237 in detail.

What is ISO 9237?

It is a method for testing fabric’s air permeability. It can be applied to various fabrics, including woven, nonwoven, and industrial fabrics used for technical reasons. In this method, the airflow rate passing perpendicularly through a given area of fabric is measured. The pressure difference throughout the fabric test area and time has already been determined. Nowadays, air permeability testers are highly advanced as they require the machine to start and provide airflow values.

Apparatus for ISO 9237

• Air Permeability Tester
• Fabric Specimen
• Fabric test plate

Sample Preparation for ISO 9237

• Take a sample of at least 1m in length and full width.
• Usually, samples don’t need to be cut in any specific size for air permeability tests.
• Take at least 3 samples or as desired.

Conditioning of Samples for ISO 9237

• Condition samples at standard atmospheric conditions for about 4 hours. i.e. 20 ± 2°C and 65 ± 4% relative humidity.

Testing Procedure of ISO 9237

• Turn on the tester. (Figure 1)

  

• Select sample size. In this standard, 20cm2 is chosen as the test area. (Figure 2)
• Set the pressure difference. Usually, 100Pa is enough for clothing purposes, while for industrial usage, it is 200 Pa. Pressure should be constant throughout the test. Choose the difference according to fabric end-use.
• Select the desired test unit.
• Select standard from the tester pre-load standards library.
• After setting the parameters, place the test specimen on a circular sample holder. It should be wrinkle-free and without any distortion. (Figure 3)
• Start the test by giving a command.
• The screen displays the amount of airflow. Record the reading. (Figure 4)
• Repeat the test process at different locations under the same conditions.
• Take average measurement of each test sample.

Report Formation of ISO 9237

• State details about the specimen’s material. (e.g., knit or woven, yarn type, weave, etc.). These details have significant importance as these parameters directly influence test results.
• The test surface area under the clamp is where the test is performed.
• State the number of test samples.
• Also, mention that the test is performed under ISO 9237.

Insights and Experience

• Always mention the sample side on the test report. Some fabrics have different permeability values on the face and back of the fabric.
• The fabric should not be clamped in a stretched state because it will allow more air to pass, which affects the results.

Conclusion

In conclusion, air permeability is a deciding parameter in the physical testing of fabrics. Technical fields, including medical, sportswear, and performance, need fabrics to have a high level of comfort and be breathable. Some other fabrics like raincoats, outdoor traveling tents, and some medical fabrics need low air permeable fabric for resistance against wind and moisture. In these fabrics, safety purpose is prioritized over comfort. Fabrics used in the medical industry require low air permeability to avoid moisture and stop growing bacterial fungi. So, you must decide prior to testing depending on the end use of fabric. Check about DaRong Air Permeability Tester!

 FAQs

1. Which fabric has the best air permeability?

Air permeability depends on several parameters. Usually knitted and fabrics having loose structure shows good air permeability.

2. What is an air permeability unit?

It is expressed in cubic feet per minute (CFM) and cubic meters per minute (CMM). A higher value shows higher air permeability.

3. What is a good air permeability value?

The most suitable air permeability value for fabrics used in clothing generally falls between 10- 20 CFM. However, the permeability rating of protective clothing is below 5 CFM.

4. What factors affect the air permeability of fabric?

Air permeability is affected by a variety of parameters, including

1. Thickness of yarn
2. Weave Structure or design pattern in non-woven
3. Number of yarns per inch
4. Amount of twist in yarn
5. Cloth thickness and weight

     5. Why air permeability is important?

Air permeability is crucial in determining the performance of fabrics used in technical industries like protective clothing, medical fabrics, and filtration. These fabrics must meet particular air permeability standards to ensure they are working.

Related Resources

ISO 9237 Fabric Air Permeability Tester YG(B)461EC

Air Permeability Tester

An Ultimate Guide to Air Permeability of Fabric

ASTM D737: Practical Tips on Air Permeability of Textile Fabrics Test Method