EtO Sterilizer Validation

Sterilization with EtO is a low-temperature process, typically between 37 and 63°C, that uses Ethylene Oxide gas to reduce the level of infectious agents. EtO is used on gas form and usually mixed with other substances, such as CO2 or steam, and is mainly used on products that cannot withstand the heat of typical autoclave sterilization e.g. plastic. The main physical parameters to be monitored are temperature and relative humidity.

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 and a five phase cycle. The difference being that a three phase cycle does not consider the pre and post exposure phases. 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, allowing EtO gas to be desorbed. This process can be in a separate chamber or room. Time, temperature and pressure changes are important.

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