A medical autoclave is a device that uses steam to sterilize equipment and other objects. This means that all bacteria, viruses, fungi, and spores are inactivated.
Autoclaves are found in many medical settings and other places that need to ensure sterility of an objects. Many procedures today use single-use items rather than sterilized, reusable items. This first happened with hypodermic needles, but today many surgical instruments (such as forceps, needle holders, and scalpel handles) are commonly single-use items rather than reusable. See waste autoclave.
Because damp heat is used, heat-labile products (such as some plastics) cannot be sterilized this way or they will melt. Some paper or other products that may be damaged by the steam must also be sterilized another way. in all autoclaves, items should always be separated to allow the steam to penetrate the load evenly.
Autoclaving is often used to sterilize medical waste prior to disposal in the standard municipal solid waste stream. This application has grown as an alternative to incineration due to environment and health concerns raised by combustion by products from incinerators, especially from the small units which were commonly operated at individual hospitals. Incineration or a similat thermal oxidation process is still generally mandated for pathological waste and other very toxic and/or infectious medical wastes.
There are physical, chemical, and biological indicators that can be used to ensure an autoclave reaches the correct temperature for the correct amount of time.
Chemical indicators can be found on medical packaging and autoclave tape, and these change color once the correct conditions have been met. This color change indicates that the object inside the package, or under the tape, has been processed. Biological indicators contain spores of a heat-resistant bacterium, Geobacillus stearothermophilus. If the autoclave does not reach the right temperature. when incubated the spores will germinate, and their metabolism will change the color of a pH-sensitive chemical.
Some physical indicators consist of an alloy designed to melt only after being subjected to the relevant holding time. If the alloy melts, the change will be visible.
Some computer-controlled autoclaves use an F0 (F-nought) value to control the sterilization cycle. F0 values are set as the number of minutes of equivalent sterilization at 121 or 249 degree Celsius. Since exact temperature control is difficult, the temperature is monitored, and the sterilization time adjusted accordingly.