Which sterilisation method is represented by ethylene oxide?

• A. Gas radiation
• B. Ethylene oxide (chemical)
• C. Moist heat
• D. Dry heat

Answer: (B)

Ethylene oxide is a chemical gas sterilant used for sterilising equipment that cannot withstand high temperatures. It works by alkylating proteins and nucleic acids in microorganisms, effectively destroying bacteria, spores, and viruses at relatively low temperatures. Because residual gas is toxic, aeration after exposure is required to remove the sterilant from instruments. This sets it apart from physical methods like moist heat (steam) and dry heat (hot air), which rely on high temperatures rather than chemical action. It also isn’t described as radiation-based sterilisation. So, the method represented by ethylene oxide is chemical gas sterilisation.