Ethylene oxide or ETO sterilizers are widely used in the pharmaceutical industry and health care institutions to sterilize products/materials sensitive to moisture or heat. These high technology sterilizers are potent in killing pathogens and consist of electrical heating jackets and provide excellent steam and temperature distribution in the heating chamber. The heating chamber is generally made of stainless steel and enclosed with aluminum or stainless steel panels. The machines are also equipped with automatic temperature control mechanism. In ETO sterilization bacteria die from the coagulation or denaturation of the protein constituents.
The total length of the process can vary depending on the goods to sterilize, but typical cycles are between 36 and 48 hours. There are two main ways to divide the cycle; a three phase cycle A typical 3 phase EtO sterilization cycle can be summarized as follows;
| Stage | Purpose |
| Preconditioning | Provides temperature and humidity conditions to incentive infectious agents to come out of hibernation. |
| Sterilization / Conditioning | Exposure to the sterilizing agent at the specified temperature, RH and pressure. |
| Aereation | Removal of EtO gas using changes of air in sterilization chamber, allows EtO gas to be desorbed. This process can be in a separate chamber or room. Time, temperature and pressure changes are important. |
