Ethylene Oxide Sterilization process
It is one of the most effective sterilization process at low temperature, and has more than 60 years of existence in the medical and pharmaceutical fields. Nowadays, the EO sterilization process has been developed until reaching a high level of performance and efficiency. It is now a well proven technology for thermo-sensitive products, unable to be sterilized by others traditional sterilization methods like steam or dry heat process.
That chemical sterilization process is based on a large gas diffusion (ethylene oxide or EO) able to annihilate the micro-organisms, is a low temperature sterilization method as it is usually used up to 60ºC. Thanks to this important advantage, delicate products can be treated like syringes, latex gloves, catheters, etc….
What is the ethylene oxide (EO)?
The Ethylene Oxide is a colorless and odorless gas, which the chemical properties allow:
- An excellent propagation into the porous materials.
- A high diffusion and absorption on the thermo-sensitive products (mainly plastics).
- A preservation of the material characteristics.
Thanks to those specifications, Ethylene Oxide (ETO/EO) is able to:
- Spread into creases and difficult access to be sterilized.
- Sterilize between 25ºC and 60ºC (low temperature) ensuring neither deformation nor destruction of the sterilized elements.
- Go across wrapping membranes that contain the product.
For the Ethylene Oxide sterilization (ETO), different EO mixture could be used:
*Ethylene Oxide with CO2: the EO is mixed with X% of CO2, due to their mixable properties. In addition, they have the same molecular weight. The high vapor pressure of the CO2 makes that the higher CO2 concentration in the mixture is, higher the pressure is inside the EO container/drum. In other words, the pressure inside the sterilizers would be higher in order to maintain a correct EO concentration.
*100% Ethylene Oxide: that mixture allows to work at a lower pressure inside the sterilizer. Generally, the use of one or the other mixture depends on the gas availability in every country.
RSD uses to work with 100% Ethylene Oxide (100% ETO + N2), or with 90%ETO + 10% CO2 mixture, because of the following advantages:
- Low pressure cycles <0,5barg, giving the advantage of a safer design, as the sterilizer is not considered anymore as pressure vessel (PED 2014/68/UE).
- Stable and safe process, according ATEX directive 2014/34/UE.
- Environment concern, using less CO2.
- More economical cycles, as less gas is required to reach the EO concentration necessary.
How does the Ethylene Oxide (EO / ETO) sterilization process work?
This gas is toxic, inflammable and explosive. That’s why it is important to handle the process under precaution, working with sterilization equipment that can ensure the personal and installation safety, as well as the environment concerns.
For these reasons, special attentions should be taken for ethylene Oxide cycle development. Always looking for the best relation between the following variables: Gas concentration, humidity, temperature and exposure time.
Ethylene Oxide sterilization processing consists of 3 phases:
1 - Conditionning or Pre-conditioning phase
During this phase, the micro-organism growth has to be stimulated, using temperature and humidity.
- Conditioning: if it is carried out inside the sterilizer.
- Preconditioning: if it is done out of the sterilizer, in a separate room.
The working conditions are generally 30-60% RH, 30-60ºC, at atmospheric pressure.
2 - Sterilization phase
The product should be sterilized thanks to an appropriate and validated cycle, with the following requirements (non-exhaustive list):
- Control of the physical parameters in any cycle phase (Pressure, Temperature, Humidity and Time).
- Inflammability diagram control to prevent having any unsafe atmosphere inside the chamber.
- External elements like ventilation room, monitoring system (LEL, PPM), utility availabilities, etc.
- Air purification system control, to avoid sending high and/or low concentration of ethylene oxide to the atmosphere. The technology used uses to depend on the local laws, as well as the final user budget. We can choice between the technology Scrubber or the catalytic system.
3 - Ventilation or Aeration phase
This phase consists in ventilate the product sterilized, taking out all the EO residual particles from the cardboard, wrapping and product. It could be done either in the sterilizer or in a separate room called degassing room. The degassing time depends on the kind of material used on the product and its capacity to release the gas.
The working conditions are generally 30-60ºC, at atmospheric pressure (with a slight negative pressure to avoid EO contamination to the sterilization building).
The Key parameters of this sterilization process
During the whole process, there are key parameters that must be controlled until the end of the cycle, which also allow the process optimization:
- Gas concentration.
- Chamber temperature.
- Relative humidity.
- Exposure time.
What material can be used with EO process ?
That sterilization process is used in the medical and pharmaceutical fields. The elements that use to be sterilized with Ethylene Oxide are all the materials that can’t be sterilized by traditional methods. In other words, all the thermo-sensitive material.
Some examples of those materials: Wrapping, plastic products, raw materials, surgical, medical and optical instrumentation, prosthesis, etc….
The ETO sterilization is nowadays, without any doubt, one of the most effective sterilization method for thermo-sensitive products, and takes importance where traditional methods are limited. In other word, this method is one of the most sought for medical device treatment.
What are the advantages of Ethylene Oxide (EO / ETO) sterilization?
- High efficiency as antivirus, bactericide and fungicide.
- Ideal for thermo-sensitive materials, thanks to the low temperature sterilization cycle, ensuring neither deformation nor destruction of the load.
- High diffusion coefficient in wrapping, creases, basically in any difficult access area.
- Process that doesn’t alter physical qualities of the sterilized product.
Why RSD for EO sterilization process?
Thank to its high experience and its know-how, RSD provides safe and reliable Ethylene Oxide chambers and EO process.
As specialist in Ethylene Oxide Sterilization Process RSD® offers
- Ethylene Oxide Sterilizers
- Consulting and services for EO process
- Contract EO sterilization services