Autoclaves and sterilizers are devices that are used to disinfect medical instruments. Steam sterilizers (aka autoclaves) are the most common type of sterilizer and use elevated temperature and pressure to disinfect medical equipment. Dry heat sterilizers simply heat the item to a temperature where biological organisms are destroyed, while gas sterilizers use a substance like Ethylene Oxide that destroys microorganisms through a chemical reaction. Desktop sterilizers, commonly used in doctors' offices and clinics, are small enough to be placed on tabletops, while freestanding sterilizers can be taller than their human users and are commonly used in large healthcare facilities.