Water vapour transfer in waterproof breathable fabrics

Investigates whether water vapour transfer from the local environment of the human body at a relative humidity less than 100 per cent to a rainy or wind‐driven environment of relative humidity almost 100 per cent is possible. To identify whether prolonged rain has an effect on water vapour transfer in waterproof breathable fabrics, secondary experiments were carried out using a precipitator simulator covering a large area with severe rain. It was found that waterproof breathable fabrics breathe even under rainy conditions (with lower water vapour transfer rate), though encountering limitations under prolonged severe rain. The water vapour transfer rate was reduced under wind‐driven rainy conditions. More condensation was observed under rainy conditions on all fabrics except PTFE laminated fabrics.