Ethylene oxide is a colourless gas with a sweet odour; it is a colourless liquid below 10 deg C. It is an EXTREMELY FLAMMABLE GAS. The gas is slightly heavier than air and may spread long distances. Distant ignition and flashback are possible. The liquid can accumulate static charge by splashing or agitation. Ethylene oxide can decompose explosively. Cylinders and closed containers may rupture violently if heated. It is a COMPRESSED GAS. It is also DANGEROUSLY REACTIVE. Ethylene oxide may polymerize or decompose violently when exposed to high temperatures or contaminants (e.g. acids and metals). Ethylene oxide is VERY TOXIC and may be fatal if inhaled. It is irritating to the respiratory tract and is a central nervous system depressant. This means that high concentrations may cause headache, nausea, dizziness, drowsiness, and incoordination. Solutions cause skin irritation and probably cause eye irritation. Ethylene oxide is a CANCER HAZARD - it can cause cancer, based on human information. It is also a POSSIBLE REPRODUCTIVE HAZARD (it may harm reproductive capability, based on animal information) and a MUTAGEN (it may cause inheritable genetic damage).

The major use is as a chemical intermediate for the manufacture of other chemicals. As a non-explosive mixture with nitrogen or carbon dioxide, it is used as a sterilizing agent for medical devices and surgical instruments in hospitals, as a disinfectant and as a fumigant.

Ethylene oxide (EO) is a high purity chemical (99.7% or higher). Impurities may include acetaldehyde, acetic acid, acetylene, and inorganic and organic chlorides. It is also available as an non-flammable mixture with nitrogen or carbon dioxide. Historically, mixtures with dichlorodifluoromethane (Fluorocarbon 12) were available, but environmental concerns have led to the use of other flame retardant diluent gases. EO is shipped as a liquid under its own vapour pressure of 50 kPa at 21.1 deg C in compressed gas cylinders, special containers, such as insulated steel drums, portable tanks or insulated single-unit tank cars.

Ethylene Oxide is also known as Dihydrooxirene, Dimethylene oxide, EO, ETO, 1,2-Epoxyethane, Epoxyethane, Ethene oxide, Oxacyclopropane, Oxane, Oxidoethane , Oxirane, Oxyde d'éthylène.

Its CAS Registry Number is 75-21-8. This number is assigned by the Chemical Abstracts Service (CAS) in the United States and is used as a unique identifier number world-wide.