Test Procedure for Air Permeability of Textile Fabrics

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.

Air Permeability Testing Apparatus accurately and swiftly determines the resistance of fabrics (woven, knitted and nonwoven textile) to the passage of air (air flow) under constant pre-set air pressure while firmly clamped in the test rig of selected test head/area. The air permeability of the fabric is calculated automatically within a short time.

Air Permeability Test Procedure

1 Test the conditioned specimens in the standard atmosphere for testing textiles, which is 21 +/- 1°C (70 +/- 2°F) and 65 +/- 2 % relative humidity, unless otherwise specified in a material specification or contract order.

2 Handle the test specimens carefully to avoid altering the natural state of the material.

3 Place each test specimen onto the test head of the test instrument, and perform the test as specified in the manufacturer’s operating instructions.Place coated test specimens with the coated side down (towards low pressure side) to minimize edge leakage.

4 Make tests at the water pressure differential specified in a material specification or contract order. In the absence of a material specification or contract order, use a water pressure differential of 125 Pa (12.7 mm or 0.5 in. of water).

5 Read and record the individual test results in SI units as cm^3/s/cm^2 and in inch-pound units as ft^3/min/ft^2 rounded to three significant digits.

FPIQ 10.5.1 For special applications, the total edge leakage underneath and through the test specimen may be measured in a separate test, with the test specimen covered by an airtight cover, and subtracted from the original test result to obtain the effective air permeability.

6 Remove the tested specimen and continue as directed in 10.3-10.5 until ten specimens have been tested for each laboratory sampling unit. When a 95 % confidence level for results has been agreed upon in a material specification or contract order, fewer test specimens may be sufficient. In any event, the number of tests should be at least four.