Ethylene oxide (EtO) is used to sterilize heat sensitive hospital equipment. EtO readily reacts with biological organisms and is commonly used for sterilizing. The sterilant gas (composed of EtO and sometimes a diluent gas) is injected into a chamber exposing the desired materials to the sterilant gas. After the sterilizing time is complete, the sterilant gas is usually vented to a control device. The diluent gas may be composed of CFC’s, HCFC’s or CO2. Most local facilities using sterilizers are required to comply with District Rule 1203 and/or the federal NESHAP which requires EtO controls.