In presence of gaseous hydrocarbons (methane, acetylene, ethane and ethylene), the infrared (IR) spectrum of poly(phenylene oxide) PPO membrane has changed at particular bands. When air or helium gas is passed through the PPO membrane sample treated by gaseous hydrocarbons, the IR spectra regained its original shape and intensity. Thus, this phenomenon is reversible and suggests the formation of an unstable complex by the physical interaction between PPO molecules and physically adsorbed gaseous hydrocarbons. Methane and acetylene reacted or affected the PPO IR spectra in the same position. while ethylene in a different position. Ethane's effect on IR spectra of PPO was similar to that observed for ethylene. It was further observed that the physical interaction between the gaseous hydrocarbons and PPO molecules possesses kinetic characteristics, i.e. depends on time and gas partial pressure, The molecular weight of PPO and the solvent (used in casting solution) boiling point affect the extent of interaction of these gases with polymeric membranes. A plausible kinetic model has been presented.