A hot air oven is a piece of electronic equipment used to sterilize items. It is often found in hospitals, where medical professionals use it to sterilize surgical equipment. Scientists and laboratory technicians also use it frequently because a hot air oven doesn't experience the same internal pressure buildup that other sterilizing equipment, like an autoclave, does.
The interior of a hot air oven contains a digital thermostat that controls the temperature, which usually ranges anywhere from 122° F (50° C) to 572° F (300° C). The oven itself is created from a double-walled construction that is designed to hold in heat and reduce energy output. The exterior of the unit is composed of metal, and the interior is made of a poor conductor. In between is an air-filled space that provides additional insulation. Inside the unit, heat is distributed evenly through the help of a built-in fan.
Compared to other types of sterilizing equipment, hot air ovens are fairly compact. The dry heat created by the ovens may not be as beneficial in killing harmful organisms as moist-heat-producing ovens are. Temperatures in this type of oven are usually comparable to those found in other sterilizing units, however. Furthermore, the cycle in a hot air oven is usually much shorter when compared to steam sterilization units.
These ovens must be preheated before they can be operated properly. The preheating time is essential for the complete sterilization cycle to be effective. Opening the chamber door before it has finished heating up lets heat out and requires the unit to be shut down completely and the preheating process to start over again.
A conventional hot air sterilization oven runs a typical cycle at 320° F (160° C). At this temperature, it takes approximately 90 minutes for the unit to complete its cycle. There are also convection hot air ovens, which use forced air at 374° F (190° C) to shorten the cycle time. Equipment wrapped in a heat-safe material can be sterilized in a convection oven in about 12 minutes. Unwrapped items take only about 6 minutes to sterilize.
Due to the high temperatures inside hot air ovens, only certain materials can be used with them. Powders and glassware are usually able to withstand the extreme heat, as are pieces of surgical equipment that would rust in a moist air oven. Other types of laboratory and medical equipment, including metal impression trays, rubber or plastic-based items, and linens, can be destroyed inside a hot air oven, however.