EN31092 Breathable

Resistance to water vapour (RET).

Test method: A porous sheet electrically heated at 35ºC, is covered (body temperature) with a membrane that is impermeable to liquid water but permeable to the vapour water (cellophane). The water provided in the hot sheet  is evaporated and passes through the membrane as vapour,  so that the liquid water does not come into contact with the fabric placed over the membrane. The perspiration is known as the heat flow needed to keep the sheet at 35ºC temperature.

The water vapour resistance resulting from the fabric is calculated by subtracting from this one, the value of the water vapour resistance obtained in the same conditions but without any fabric.