Ethylene Oxide ProcessingEthylene Oxide Processing

Ethylene oxide (also known as EO or EtO) processing is widely used for the sterilization of healthcare devices and instruments. The process involves exposing products to ethylene oxide gas under vacuum in a sealed chamber. EO sterilization assures that a safe and sterile product will be delivered to the market each and every time.

What is Ethylene Oxide Processing?

eo-chamberEthylene oxide sterilization is a chemical process consisting of four primary variables: gas concentration, humidity, temperature and time. EO is an alkylating agent that disrupts the DNA of microorganisms, which prevents them from reproducing. The EO penetrates the breathable packaging and sterilizes all accessible surfaces of the product to render products sterile by alkylation of proteins essential for cell reproduction.

What is Ethylene Oxide Used For?

Ethylene oxide can penetrate multiple layers of breathable packaging, making it suitable for the sterilization of a wide range of materials not compatible with other methods of sterilization:

  • Assembled complex devices
  • Catheters
  • Custom procedure packs
  • Equipment with integrated-electronics
  • Multi-lumen tubing products
  • Stents
  • Wound care dressings

When selecting a sterilization partner, manufacturers need to choose a contractor who has the flexibility and technical capability to meet the demands of the specific devices.

The Ethylene Oxide Sterilization Process

The ethylene oxide sterilization process may take place within a traditional ethylene oxide sterilization cycle or through our exclusive EOExpress® expedited processing cycle*. Both options consist of three processing phases. (*available at select locations).

  • Pre-conditioning: Used to preheat and humidify product loads to predefined conditions. This will assure a repeatable EO sterilization process regardless of pre-processing load storage conditions
  • Sterilization: Performed using process phases specifically designed to provide the required level of EO exposure to assure sterility for a device or family of devices
  • Aeration: Used to accelerate out gassing of exposed product loads and to contain and eliminate residual EO emissions to ensure that it meets specified residual limits outlined in ISO 10993-7

The STERIS AST Ethylene Oxide Sterilization Offering

Through our TechTeam® experts and global network of ethylene oxide locations, STERIS AST is able to offer Customers:

  • Sustainable EO sterilization services
  • Varying sizes of chambers
  • Large portfolio of cycles
  • Large range of encompassing solutions
  • Complete geographic coverage to meet your contract sterilization needs
  • Cycle optimization
  • Improved turnaround times
  • Flexible validation options
  • Parametric release
  • Research & development chambers
  • Reduced incubation studies

View our TechTeam Resources to learn more about the ethylene oxide sterilization process.

Ethylene Oxide Summary

Ethylene Oxide icon


Ethylene oxide sterilization uses a 3-part gas process which includes pre-conditioning, sterilization, and aeration

Technology Variables

  • Exposure Time
  • Temperature
  • Humidity
  • EO Concentration
  • 100 % EO Or Positive Pressure Process
  • Chamber Size
  • Single Chamber Or Multi-chamber Process

Product Considerations

    • Very few compatibility concerns; liquids generally not recommended. Packaging must be breathable
    • Impacts the concentration and exposure time
    • EO produces significant heat and humidity
    • Gas must reach surfaces requiring sterilization

Possible Effects


Due to accumulation of EO residuals products may require prolonged aeration

Exposure Time


    • (depends on validation approach and time required for degassing)


As a global leading sterilization and decontamination specialist, STERIS AST has over 40 years experience in providing safe and effective ethylene oxide sterilization.

Contact our team of experts to find out more about our Global Contract Sterilization Services