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1.1 This test method covers the quantitative measurement of thermal effusivity of woven, knitted, or non-woven fabrics using a guarded modified transient plane source (MTPS) instrument.4 This test method is applicable to a wide range of thicknesses; however, the thickness of the specimen must be greater than the penetration depth of the heat flux during the measurement time.

1.2 This test method is comparative since specimens of known thermal effusivity are used to calibrate the apparatus at the factory level. Thermal effusivity of the calibration specimens are confirmed through calculations that use established properties of thermal conductivity, density, and specific heat.

1.3 This test method is intended for measuring fabrics in a dry state at ambient conditions.

1.4 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.

1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.

1.6 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

5.1 This test method measures the rate of thermal transport between a heating element and a fabric specimen. Some of the comfort properties of a garment relate to initial thermal sensations (that is, cold or warm feeling upon initial contact), where lower thermal effusivity values indicate sensations of warmth and higher values indicate sensations of coolness. The thermal effusivity of different fabrics and their initial perceived surface temperature are important to assist product developers with fabric selection.

5.2 The sensor and the test specimen being measured shall be at the same temperature for measurements at standard conditions. This test method may be applied to any fabric with a thermal effusivity in the range of 35 to 1700 Ws^1/₂/m²·K.

5.3 Air flow shall be kept at a minimum to ensure temperature fluctuations do not occur during the measurement.