An air dehydration module includes polymeric fibers for separating water vapor from air, and also includes a carbon filter material, positioned at an outlet end of the module, and within the same pressure vessel which houses the fibers. The module may generate its own sweep stream, in which case a portion of its output is directed to flow through an orifice, towards the inlet end of the module. In an alternative embodiment, the sweep gas is produced by a distinct gas-separation module, which receives an input stream from the output of the dehydration module. The dehydration module produces clean and dry air which can be used as is, or as an input stream to an air separation module.