Explain the Functionality of Hot Air Oven?

Hot air oven sterilizes the object by hot dry air. It kills the microorganisms by oxidizing cellular constituents. Dry Heat is less effective in killing microorganisms than moist heat. Higher temperature for a longer time period is used with dry air because it-

(i) Has less penetration power, and

(ii) Removes moisture from microorganisms and thus interferes with coagulation of microbial proteins.

Hot air oven can be used at different temperatures. Operating time depends on the temperatures used as highlighted in Table.

Table: Relation between temperature of hot air oven and the time period of sterilization

You would realize that the most commonly used temperature is 160° C for 2 hours. We are all familiar with hot air ovens. Hot air oven contains an insulated cabinet kept at constant temperature by electric heating mechanism and thermostat. Air keeps on circulating within the cabinet through a fan. For proper circulation of hot air, the shelves are perforated. An oven is used to sterilize glassware, corrodeable metal instruments, powder, oil etc. which can tolerate prolonged heat exposure but get spoiled by moist heat. However, it is not suitable for heat sensitive materials, like plastic and rubber items.