Gaseous agents are used when the target materials are sensitive to heat or are dry.

Ethylene oxide is a very powerful sporocidal agent used to sterilize rubber hose and other heat-sensitive materials.  This gas is very flammable, so it is generally mixed with nitrogen gas or carbon dioxide and used in special sterilizing chambers similar to the autoclave.  Ethylene oxide must be allowed to outgas before the material can be used.

 Beta-propiolactone and propylene oxide are used to sterilize bone and other compounds that are porous.  These agents are carcinogenic, so must be allowed to diffuse out of the materials as well.