2.2.1.2 Dry Heat

2.2.1.2 Dry Heat

The sterilizing effect of dry heat is due to oxidation of intracellular components and extreme dehydration. This requires very high temperature to achieve the required effect.

 Dry Heat

Dry heat is applied to sterilize materials which include glass petridishes, pipettes, flasks and metal objects in hot air oven, which is electrically heated and thermostatically controlled (oils, waxes and powder are also sterilized in hot air oven)

The operation or use of hot air oven includes

(i) the heating up period which is the time taken for the entire load to reach the sterilization temperature

(ii) the holding period – the time taken for complete sterilization which is normally about 1 h at 160oC or 2 hours at 140 oC and

(iii) the cooling down period, the time required for gradual fall of temperature (usually 2 h or more).

The temperature should be brought down to less than 80oC before opening the oven to prevent glasswares from cracking as a result of too rapid fall in temperature.

Last modified: Saturday, 31 December 2011, 5:26 AM