Working with Ethylene Oxide Sterilization

Disinfection is serious business, especially now during the COVID-19 global pandemic, when the need to disinfect and sterilize everything from offices to ventilators is so important. This article is about ethylene oxide, a frequently used but potentially hazardous sterilizing agent.

Ethylene oxide has been used for decades. In fact, in 1977, the National Institute for Occupational Safety and Health (NIOSH) estimated that with more than 10,000 sterilizers in use, 75,000 workers nationwide were potentially exposed. However, during the period 1994 to 1998, ethylene oxide was associated with 10 explosions causing major property damage and scores of injuries, including at least one fatality. As recently as August 2004, a major contract sterilization company had an explosion in their facility, injuring four employees and shutting down the plant.

Abbreviated as EtO (or less commonly EO), ethylene oxide is used for sterilization in many medical, dental, veterinary, and animal surgical facilities. This is because it is efficient and performs at low temperatures compared to steam sterilization. In addition, EtO is very compatible with the polymer-based single use medical devices, procedure kits, and surgical trays, as well as most surgical instruments.

Ethylene oxide is a gas at room temperature with a boiling point of 10.7°C (51°F) and flammable limits in air from three to 100 percent, a very wide range. The vapor density is one and a half times that of air, therefore the vapors will tend to sink to the floor (or lowest available levels) and accumulate, spreading to the nearest ignition source.

EtO is also a serious health hazard. It is colorless with a characteristic sweet, ether-like odor. However, be warned—if you can smell it, you are breathing a toxic concentration hundreds of times greater than the exposure limit, given the OSHA occupational permissible exposure limit is only 1 ppm for a regular eight-hour work shift and the reported odor threshold is between 500 and 700 ppm. Therefore, odor is a very poor warning property for EtO.