Method and apparatus for sterilizing vapor.

A method of sterilizing an enclosure sealable, comprising the steps of circulating a carrier and sterilizing gas through the enclosure and through a flow path having an outlet from the enclosure and an inlet to the enclosure, making any sterilant in the gas flow received from the enclosure is suitable for disposal, and the content of water vapor, after which the gas flow is heated and further sterilant is added to sterilize the enclosure, characterized in that the flow path has two parallel branches, in one of which the sterilant in the gas flow is made suitable for disposal and any content of water vapor in the gas is reduced, and the other of which the carrier gas is heated and sterilant is added to the gas, the method further comprising the steps of initially circulating said carrier gas through said one branch, monitoring the moisture content of the gas in the enclosure and terminating flow of carrier gas through said one branch when the relative humidity in the enclosure has been reduced to a predetermined level, so that the surfaces of the enclosure are relatively dry, initiating flow carrier gas through said other branch and adding a sterilant vapor or vapors to the gas passing through the other branch until condensation of the sterilant in the chamber takes place, terminating the supply of sterilant to the carrier gas, continuing to circulate the gas substantially saturated with sterilant carrier, for a predetermined to ensure sterilization of the room time, terminating flow through said other branch and redirecting the flow of carrier gas through said one branch to extract the sterilant from the gas enclosure to make the sterilant suitable for disposal and to reduce moisture re Lativa carrier gas.