Principle:
The steam has more penetration power than dry heat and thermal capacity of steam is more than thermal capacity of dry heat.
The method is useful for killing of bacterial spores.
The moist steam penetrate the spores and capsules of bacteria, rupture it and
Escaping protoplasma it coagulated.
The temperature conditions for autoclaving:
1 1150C to 1180C for 30 min.
2 1210C to 1240C for 15 min.
3 1260C to 1290C for 10 min.
4 1340C to 1380C for 5 min.
Working:
A sufficient quantity of water is poured into the chamber after removing the perforated basket.
The level of water adjusted in such a way that it should not touch the bottom of perforated basket.
The material is placed in the basket and it placed in the autoclave.
Close the lid with wing nuts and bolts.
Switch on the heater.
Vent is opened and safety valve is set to required pressure.
When steam comes out for 5 min, then close the vent, the steam pressure stats rising it should be maintained to required level.
After the stated time, switch off the autoclave.
Allow to cool to about 40oC.
Open the vent and allow the complete steam to pass from autoclave.
Lid is opened and sterilized material is taken out
Use:
Sterilization of surgical dressings and surgical instruments.
Sterilization of containers and closers.
Sterilization of official injections
Principle:
Moist heat sterilization is a method of sterilization in which steam is used for sterilization.
The steam has more penetration power and more thermal capacity than dry heat.
The steam penetrates the spores & capsules of bacteria causing rupture and coagulation of protoplasm.
Working:
A sufficient quantity of water is poured into the chamber after removing the perforated chamber. The level of the water is adjusted in such a way that it does not touch the bottom of the perforated chamber. The lid is then closed with wing nuts and bolts. The autoclave is switched on to heat the water. The vent is opened and safety valve is set at the required pressure. When steam starts coming out from the vent and it continues for 5 minutes, it is then closed. The steam pressure starts raising and it comes to the desired pressure i.e. 10 lbs/sq inch with corresponding temp 115 0C or 15 lbs/sq inch with corresponding temp 121 0C After the stated period, switch off the autoclave. Allow it to cool to about 400C before opening the vent. When whole of the steam is removed, the lid is opened and the sterilized material is taken out.
Applications:
oThe method is used for sterilization of surgical dressings and surgical instruments.
oThe plastic containers and rubber closures are sterilized by autoclaving.
o Used for sterilization of a majority of official injections and eye drops.