EO Control Systems Gamma Control Systems Sterilization
 
 

Ethylene Oxide Sterilization - Process Considerations

During the sterilization process, the control system monitors various readings from such devices as thermocouples, pressure transducers, ethylene oxide sensors and humidity sensors. Certain conditions may arise that will place the process on Hold, such as:

  • Ethylene oxide tank empty during injection
  • EO injection temperature out of specification during EO inject phase
  • Pressure out of range
  • Phase condition out of range
Humidity

Humid conditions, achieved by injecting steam into the chamber, accelerate the sterilization process and make it more effective. To protect the product, condensation warnings and alarms are issued based on the temperature setpoint and partial pressure of steam. Excessive condensation can also interfere with sensor readings, therefore it is crucial that the control system monitor condensation levels throughout the sterilization process.

Temperature

Temperature monitoring is an important consideration during the sterilization process in order to ensure overtemperature does not occur. Overtemperature conditions in the chamber can damage product. As a result, product temperature thermocouples, as well as chamber temperature thermocouples, are used to ensure temperature is within acceptable ranges. It is also important to ensure chamber temperature is not too low in order to maintain the vapour state of ethylene oxide. Ethylene oxide is known to liquify at 10.6°C (51°F) standard temperature and pressure. The temperature in the chamber can also ultimately affect sterilization efficiency as well as the overall sterilization time.

Vacuum

Placing the chamber under vacuum is an important aspect of ethylene oxide sterilization because the pressure difference achieved causes more effective ethylene oxide absorption/diffusion into the product. Although achieving a vacuum in a chamber can be time consuming for large chambers, it ultimately reduces overall sterilization time by increasing the concentration at which condensation occurs as well as allowing for higher ethylene oxide concentrations.

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