Sterilizing gases are typically used when exposure to other methods (heat or radiation) could damage the materials or equipment.  The most common gases used for sterilization include ethylene oxide (EO), ozone, mixed oxides of nitrogen, and chlorine dioxide.  According to USP, “EO’s ability to penetrate through polymers, cellulosics, and other materials allows it to be used for the terminal sterilization of medical devices in their final packaging.”