EO Sterilization Process

In the past, High Temperature Sterilization Methods were used to disinfect and clean products in almost all industries. However, the heat may cause damage to products from various industries, therefore, a new process of sterilization was introduced; steam sterilization. Even the steam sterilization is not suitable for industries such as health. It can kill bacteria, fungi and spores, but it cannot be applied to all materials and instruments. Therefore, low temperature sterilization methods were explored to avoid damage caused by heat and moisture.

Many advanced medical instruments are delicate and sensitive to heat or moisture. Therefore abovementioned processes cannot be applied on them for the purpose of sterilization because heat or moisture can damage them. The alternative for heat and moisture sensitive equipment is EO sterilization.

EO Sterilization

Before proceeding any further, let us put it out here that EO sterilization should only be used for those products which cannot be sterilized using an alternative method. Since EO sterilization relies on using poisonous gases, it should only be applied if the products are sensitive to moisture and heat. Poisonous gases which kill micro-organisms, can be lethal to humans as well.

EO (Ethylene Oxide) is a colorless toxic gas commonly used for low temperature sterilization. It targets the cellular proteins and nucleic acids of microorganisms. It is ideal for sterilizing instruments with long lumens such as endoscopes, because it cannot withstand the higher temperature sterilization.  Hence, EO sterilization is used as its low temperatures, from 25 – 55°C, can effectively kill micro-organisms. If you decide to pick a lower range of temperature, you might need to a longer exposure time, for effectiveness.

EO Sterilization Cycle

The process of EO sterilization comprises of at least three stages:

1. Preconditioning

In the initial stage of EO sterilization, the chamber environment is prepared to comply with the ideal conditions for temperature, pressure and humidity. This is known as preconditioning. At this stage, vacuum is created by removing air from the chamber so that gas can be allowed to enter. To make sure that the staff and environment are safe, first a leakage test is performed. This guarantees that the staff won’t be exposed to the process. As EO is only effective in a humid environment, small amount of steam is injected into the chamber to humidify the area. Further, steam or hot water, found in the jacket, is used to heat up the chamber. To reduce temperature fluctuations, the temperature of jacket is kept the same.

2. Sterilization

Once the environment is ready, the actual sterilization process can be carried out. In this stage, the EO gas, along with certain amount of steam, enters the chamber via evaporation. The presence of steam ensures that humidity level remains up to carry the EO to all parts of the load. After achieving the required concentration in the chamber and the load, the stage of sterilization begins. If the gas concentration level in the chamber is low, there is need for longer exposure of the gas to effectively sterilize the instruments. The concentration level has to be picked vigilantly, because many kinds of plastics absorb EO gas. To be on the safe side, EO is introduced to the chamber after a while.

3. Aeration (Degassing)

The most important stage of EO sterilization is Aeration. It is conducted for the longest part of the whole process. The toxic gas could damage plastic material’s body tissue; therefore, aeration is carried out for the longest time to remove any EO residue, and to allow absorbed gas to evaporate from the sterilized products. Aeration is conducted by treating the load with HEPA filtered air at a temperature of 30°C to 50°C. Normally, the aeration stage lasts for 48 hours. It requires a special infrastructure comprising of a gas tight ventilation pipe directed towards the roof top or to a catalyzer. Using a medical facility’s ventilation system is strongly forbidden for this purpose because it can be dangerous. Once again, at this stage too, the ventilation piping must be tested for gas leaks to minimize the risks.

Final Words

The process of EO sterilization is risky and complicated. It requires professionalism, experience and qualification to carry out such sensitive process. The team at Dynatec labs is experienced to provide Ethylene Oxide Sterilization Services as per the requirements of the material being sterilized. To know more about our services, or to get a quote, get in touch with us today.

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