Membrane dryers are used for applications where there is limited installation space, no power source available, or explosive or corrosive conditions exist.  Air passes through the inside of a semi-permeable hollow membrane fibre where water vapour diffuses through the fibre walls. The diffusing process reduces the water content of the compressed air.

The achieved dew point depends on the inlet temperature of the compressed air and ambient temperature. The lowest possible dew point is -40 ° C.