Ethylene Oxide Sterilization Process: An Overview

Ethylene Oxide sterilization service (abbreviated as EO or ETO) is a technique that uses a colorless gas to sterilize medical equipment and industrial devices. The process uses moderate heat to increase the gas' diffusion kinetics. 

EO's microbicidal activity is via alkylation with the DNA of viruses, bacteria, yeasts, molds, and insects, thereby killing them.

EO Sterilization Process

EO sterilization is divided into three stages; preconditioning, sterilization, and degassing (aeration).


The load to be sterilized is placed in an EO sterilizer. First, the ideal chamber environment in terms of humidity, temperature, and pressure is set. Then the air is pumped out of the chamber to give room for gas penetration. 

A leakage penetration is conducted to ensure the chamber is air-tight. Since EO works efficiently in a humid environment, steam is injected to humidify the load.


After the chamber has been preconditioned, the EO gas is injected slowly into it until the required concentration is achieved. The sterilization process takes place as the gas interacts and diffuses into and out of the load. 

The gas concentration is inversely proportional to the sterilization time; hence high EO concentrations require less sterilization time. Different materials absorb the EO gas differently; hence determining and maintaining the right EO concentration and sterilization time for the load is imperative.

Degassing (Aeration)

When the sterilization process is complete, the load needs to be cleared off the residual gas. Here, high-efficiency particulate absorbing (HEPA) filtered air is circulated over the load at temperatures between 30°C to 50°C for 48 hours to rid the load of EO. 

The air is then piped to a catalyzer before being released into the environment. After successful and proper aeration, the devices are sterile and ready to be used again.

The Benefits Of EO Sterilization 

This process does not expose devices to excessive radiation, heat, or moisture. The relatively low temperatures used in the process make it more compatible with a wider variety of devices. It is safe for use on components made from various materials, like polymeric material or components containing electronic components, which may be heat or moisture sensitive. 

Since EO can permeate most surfaces and spaces, it is suitable to sterilize devices and equipment in their final packaging stage. This increases the efficiency of the process in destroying a wide range of microorganisms, including resistant spores.   

Due to the gas's non-corrosive nature, it is friendly for use on various materials such as rubber, plastic, and metal.


EO sterilization is suitable for a wide array of medical and industrial equipment. EO device sterilization services have advanced technologically with fully automated processes and auto shut-off capabilities, making the process fast, safe, and efficient.