The most common of all sterilization methods is steam. This is a nontoxic, inexpensive and sporicidal process. It rapidly heats and has the ability to penetrate fabric. Steam sterilization is achieved by exposing products to saturated steam at high temperatures (ranging from 121C to 134C), at a required pressure and for a specified time.
Requirements for this process are identified in USP, as well as ISO 17665 (Sterilization of Health Care Products – Moist Heat). USP chapter 1229.1 is titled Steam Sterilization by Direct Contact, and it covers: Saturated Steam, Gravity Displacement Cycles, Prevacuum Cycles, Sterilization Cycle Control, and Validation of Sterilization by Direct Contact.
According to USP, “Saturated steam is a biphasic mixture of H2O in gas and liquid phases in thermal equilibrium. Saturated steam has a singular temperature-pressure relationship in which both phases are present, and at a given temperature only one pressure is possible for saturation.” There are several benefits to using steam sterilization. First, saturated steam has the ability to rapidly kill any microorganisms. Second, steam can transfer its thermal energy to the items being sterilized – this enables the sterilization of all exposed surfaces.
Because of the high heat involved in steam sterilization, it is not appropriate for all materials.