EO sterilization is the most commonly used sterilization method in the medical industry, accounting for more than half of all sterilized medical packaging. EO is a colorless, flammable and carcinogenic gas, mainly used as the main component of polymers and products such as antifreeze.

The sterilization process includes pretreatment of packaging, air intake and air deflation.

Pretreatment refers to exposing the medical package to a warm, humid environment until the internal temperature and humidity evenly reach the relative humidity (approximately 45°C and 55% to 65%). The packages are then placed in a sealed environment to expose them to EO gas.

After the predetermined exposure time has elapsed, the EO gas is released. The high temperature helps to eliminate the remaining EO gas. Because EO gas needs to be able to enter the medical packaging and come into contact with the medical devices inside, and then needs to be able to be discharged from the packaging to reduce the gas concentration and thus the toxicity level.

 Therefore, if the EO sterilization method is considered, the air permeability and permeability of the packaging material when designing medical device packaging. Another thing that needs to be considered is the pressure change. The strength of the medical device packaging seal must be able to withstand the pressure change during the sterilization process, but not too strong, so as to affect the convenience of the end user to open the package.

One of the best tests to evaluate the air permeability of medical device packaging materials is the determination of ISO5635-5 air permeability. This experiment uses a device called a densitometer, which uses a cylinder that is pulled downward by gravity to pass a known volume of air through a porous material. The more porous the material, the faster the cylinder will fall off.