ETO Sterilizer

EtO sterilization is used for products that cannot withstand heat.  An example of this is a catheter.
The most important parameters in an EtO process are RH, temperature andpressure. For EtO use, it is crucial to control RH and temperature within certain limits. Vacuum (pressure) is pulled to remove air prior to the introduction of EtO making sure the EtO gas permeates the product being sterilized. 
A typical EtO sterilization cycle involves several stages and can basically proceed as follows:
Pre conditions: The product is exposed to a warm, humid environment for at least 12 hours (70%RH, 55°C) to ensure the product is at a uniform temperature andhumidity.
Exposure: Vacuum is pulled and EtO gas is introduced. The product is exposed for 4-8 hours usually. During the process the RH is kept at approx. 70% and the temperature at 55 °C.
Post conditions: The EtO gas is removed by repeatedly pulling a vacuum and then introducing air into the sterilization chamber until the EtO gas is cleared out (8-12 hours).
It should be noted that there is no standardized cycle for EtO sterilization. Generally there is a tremendous variety in exposure times and gas concentration.
The size of the sterilizers can range from small bench-top sterilizers to large rooms. Because of problems with toxicity and risk of explosion, many companies are choosing to contract out this work rather than perform it themselves. EtO use is therefore becoming very specialized and used by a small number of contract companies. A large part of all medical devices are sterilized by the EtO method.