Applications of the Trace Gas Technique in Clothing Comfort

Abstract

A laboratory appartus employing a trace gas technique has been developed to systematically study the effects of fabric and garment properties on microclimate ventilation in a simulated garment assembly. Nitrogen was used to flush the microcli mate enclosure, and the rate of atmospheric oxygen build-up in the system was traced. The gas exchange was assumed to have first-order kinetics. A new parameter, areal ventilation rate, that takes into account the microclimate volume and the fabric surface area, has been developed. External wind effects were simulated by conducting experiments in still air and in the presence of forced air flow. The results show that in still air, fabric air permeability has an insignificant effect on areal ventilation rate. However, with increasing external air flow, the effect of air permeability becomes more pronounced. Areal ventilation values are found to increase linearly with increasing external air velocities, and the influence of fabric constructional variables increase accordingly. The combined effects of permeability and air velocity on areal ventilation rate are interpreted in terms of a previously derived empirical equation. Simulation of garment openings did not have a significant effect on the ventilation rate, illustrating that small air passages are of less significance than flow through the fabric itself.

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