EO Sterilization

EO Sterilization

Ethylene Oxide Sterilization

Sterilization is a process performed to remove and destroy all living microorganisms and spores from an object. Medical devices; It can be sterilized through a variety of processes, including moist heat, dry heat, gamma radiation, UV, hydrogen peroxide, and ethylene oxide. However, medical devices are often sensitive to heat. For this reason, heat sterilization is not preferred by manufacturers.

Ethylene oxide (EO) gas, a colorless, flammable, explosive, slightly odorous and poisonous gas, was discovered in 1859. However, the bactericidal properties of EO gas 2. It was unknown until World War II. After the discovery of these properties, it was recommended as a bactericidal factor for the sterilization of heat and moisture sensitive materials and began to be used in the 1960s for medical device sterilization.

Advantages of ethylene oxide sterilization:

Disadvantages of ethylene oxide sterilization:


It is the process of preparing the device to keep the product constant at the appropriate temperature (usually 30-50 ᵒC) and 40-80% relative humidity.


Before starting sterilization, a preliminary leak test is performed under vacuum. In case of leakage or leakage, the device will not start the sterilization process. If there is no leakage, the preconditioning process begins. After the pre-conditioning process, the vacuum process is performed again and the leak test is repeated for safety. Then, the sterilization process begins with the intake of EO gas into the environment. The degassing process continues until the safe vacuum value. It uses 100% pure Ethylene Oxide (EO) or EO:CO 2 (Ethylene Oxide – Carbon Dioxide) mixture as sterilant.


Following sterilization, the products are left for a while and then washed with air. It is an important step in ensuring that no residue remains on the products.

Things to do to work safely with Ethylene Oxide:

  • EO gas is flammable and explosive. It should not be exposed to high temperature and pressure.
  • Before working with ethylene oxide, protective measures determined by the “National Institute for Occupational Safety and Health (WIOSH)” should be applied.
  • Only an authorized person and a trained person should enter the Ethylene Oxide sterilization area.
  • A danger warning sign must be displayed.
  • Ethylene oxide level must be kept under constant control.
  • An emergency action plan should be ready in case of a gas leak.
  • You should work with a gas mask and protective clothing.

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