The variables present in the sterilization process with ethylene oxide are:
- Concentration of gas: the gas is active in concentrations ranging from 300 mg/l to 600 mg/l and depending on the temperature, humidity and exposure time applied.
- Temperature: the gas is active in a temperature range that varies from 25º C to 55º C; it is important to remark that higher temperatures does not entail better results.
- Humidity: the best relative humidity (HR) to sterilize with ethylene oxide (EO) ranges from 30% to 50%. The antibacterial activity of the ethylene oxide decreases at higher HR values since the E.O. polimerizes with water and loses its action. This activity also decreases at lower HR values due to that the microorganism does not receive a good humidification and therefore the spores become more resistant to the penetration of the EO.
- ExposureTime: the times will depend on the type and size of the materials in the load; on the concentration; on the wrapping material used; on the temperature set; on the humidity value and on the initial microbial population.
In order to carry out an effective sterilization, all the above mentioned variables must keep a propper relationship between them; A change in any of the variables may cause a change in the others and as a result affect the efficacy of the sterilization process. Another fact to bear in mind once the sterilization process has concluded is the ventilation time of the sterilized material. This time may vary according to the type of sterilized material, to the wrapping type and the features of the sterilizer.