Sterilization by dry heat
Sterilization by dry heat makes use of air with a low mois-ture content that has been heated by a flame or electric heating coil. In practice, the temperature of dry heat ranges from 160°C to several thousand degrees Celsius. The dry heat kills microorganisms by protein denaturation, oxidative damage, and the toxic effect of increased level of electrolytes. Dry heat is not as versatile or as widely used as moist heat, but it has several important sterilization applications. The temperature and time employed in dry heat vary according to the particular method, but in general they are greater than with moist heat. Sterilization by dry heat includes sterilization by (a) flaming, (b) incineration , and (c) hot air oven:
Incinerators are used to carry out this process and are regularly employed in hospitals and research labs to destroy hospital and laboratory wastes.
The method is used for complete destruction and dis-posal of infectious material, such as syringes, needles, culture material, dressings, bandages, bedding, animal carcasses, and pathology samples.
This method is fast and effective for most hospital wastes, but not for metals and heat-resistant glass materials.
Thermocouples, chemical indicators, and bacteriological spores of Bacillus subtilis are used as sterilization controls to determine the efficacy of sterilization by hot-air oven.