Review of Sterilization Processes

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Dry Heat Sterilization:

Method	Mechanism of Action	Instrument / Chemical Used	Temperature	Applications
Red Heat	Burning of contaminants	Bunsen Burner	Till red hot	Inoculating loops, forceps,
Incineration	Burning to ashes	Bunsen burner or any other	Suitable temperature	Contaminated dressings, Dead bodies, bags.
Hot air sterilization	Oxidation	Hot air oven	160°C for 2 hrs.	Instruments, needles, glassware, sealed materials like oils, dry powders etc.

Moist Heat Sterilization.

Method	Mechanism of Action	Instrument / Chemical Used	Temperature	Applications
Below 100°C	Denaturation of proteins	Waterbath	65 to 75°C for 10 min	Serum, body fluids and vaccines.
At 100°C	Denaturation of proteins	Waterbath	100°C for 10 to 20 min	Glass, metal and rubber items.
Above 100°C	Denaturation of proteins	Autoclave	121°C for 15 min	Culture media, surgical dressings, equipment, solutions.

Sterilization by Radiation

Method	Mechanism of Action	Instrument / Chemical Used	Dose	Applications
Ionizing Radiations	Destruction of Nuclear Material	Cobalt60 (X Rays, Gamma Rays)	2.5 Mrad	Packaged food, antibiotics, hormones, sutures, plastic syringes, stents etc.
Non Ionizing Radiations	Damage of Nuclear Material	UV lamps, UV units.	250 -260 nm wavelength for 30 mins	Hospital rooms, Operation theaters, Laboratories

Gaseous Sterilization

Method	Mechanism of Action	Instrument / Chemical Used	Dose	Applications
Ethylene Oxide	Destruction of proteins, enzymes and nuclear material	Ethylene oxide	44 mg / lit for 24 hrs or 88 mg / lit for 2 hrs	Medical and biological preparations, catgut, plastic equipment, antibiotics.
Formaldehyde	Destruction of proteins, enzymes and nuclear material	Formaldehyde	150 gm KMno4 in 280 ml of Formalin for 1000 cu feet of room.	Hospital rooms, Aseptic areas.

Sterilization by Filtration

Method	Mechanism of Action	Instrument / Chemical Used	Pore Size	Applications
Filtration	Separation of microbes from liquids	Membrane Filter assembly	0.45 microns 0.22 microns	For sterilizing liquids, enzymes, vitamins, vaccines.