As an attractive alternative to conventional gas processes, high-flux asymmetric membranes are technically and economically suitable for a variety of industrial gas separations, including acid-gas separation from methane, hydrogen recovery, and gas dehydration. Offering greater packing density but typically lower permeation rates per unit membrane area, the newer hollow-fiber membranes are replacing the older flat-sheet configuration in commercial applications. Typical operating parameters for a spiral-wound hollow-fiber process are a temperature range of 32/sup 0/-140/sup 0/F, pressure differentials up to 1200 psi, and feed flow rates from 50,000 SCF/day to greater than 100 million SCF/day. The cellulose acetate membrane system can process mixtures containing a wide range of concentrations of hydrogen, carbon dioxide, hydrogen sulfide, water vapor, hydrocarbons, and oxygen. Minor amounts of aromatic hydrocarbons, olefins, and heavy hydrocarbons do not appear to affect the membrane performance; spiral-wound elements have already operated on gas steams containing liquid hydrocarbons without difficulty.