Ethylene oxide -carbon dioxide mixture sterilization

Ethylene oxide forms explosive mixtures in air at concentrations ranging from. f to 80% by volume. The explosion hazard is eliminated when the gas is mixed with sufUeicnt concentrations of carbon dioxide. Carhoxide is a commercial sterilant containing 10% ethylene oxide and 9()%> carbon dioxide by volume that can be handled and released in air without danger of explosion. Sterilization is aeeompiishcd in a sealed, autoclave-like chamber or in gas-impermeable bags. 

Ethylene oxide gas is highly explosive in mixtures of >3.6% vN in air, in order to reduce this explosion hazard it is usually supplied for sterilization purposes as a 10% mix with carbon dioxide, or as an 8.6% mixture with HFC 124 (2 chloro-1,1,1,2 tetrafluoroethane) which has replaced fluorinated hydroearbons (freons). Alternatively, pure ethylene oxide gas can be used at below atmospheric pressure in sterihzer chambers from which all air has been removed. 

When used as a sterilizer for medical equipment, ethylene oxide has to be handled using concentrations in carbon dioxide or a freon that are lower than 10% (the mixture would combust in air). Bases catalyse the polymerisation. 

Ethylene oxide gas is highly explosive in mixtures of >3.6% v/v in air in order to reduce this explosion hazard it is usually supplied for sterilization purposes as a 10% mix with carbon dioxide, or as an... 

Pure ethylene oxide is cheaper than gas mixtures. At one time it was used undiluted, but it is no longer possible to have this practice underwritten for insurance purposes. All existing processes, whether using pure ethylene oxide plus a diluent or using a gas mixture, operate at a positive pressure to the atmosphere. Any leakage of gas from the chamber must therefore be toward dilution in the external environment rather than toward formation of an explosive mixture in the chamber. Gas mixtures with fluorinated hydrocarbons or carbon dioxide require higher operating pressures to achieve the same sterilant concentrations as diluted pure ethylene oxide systems. 

Sterilizing. Mixtures of ethylene oxide, such as 12 percent with halocarbon-12, or 10 percent to 20 percent ethylene oxide with carbon dioxide, are commonly used in sterilization. Such mixtures require registration with the EPA. 

The Environmental Protection Agency (EPA) regulates the use and application of mixtures of ethylene oxide and carbon dioxide or halocarbon, which are used as sterilants and fumigants (7), and has established working condition limits and limit levels for allowable ethylene oxide residues in products. Ethylene oxide is also listed as a hazardous air pollutant under the flammable and toxic classes (8) by EPA s Clean Air Act. 

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