Indicators In Gaseous Sterilization

Physical Indicator: Gas concentration is measured independently of pressure rise, often by reference to the weight of gas used.

Chemical Indicator: The Royach Sacket paper is used as a chemical indicator. The indicator paper is impregnated with reactive chemical which undergoes a distinct colour change on reaction. Chemical indicators are valuable monitors of the condition prevailing at the coolest or most accessible part of a sterilizer.

Biological Indicator: They are packed in dummy packs located at strategic sites in the sterilizer. Alternatively for gaseous sterilization, these may also be placed in a tubular helix device. The species of bacteria generally used for gaseous sterilization are B. subtilis var. niger and B. subtilis var. golbigii (Table).

Table: Indicators in gaseous sterilization

Indicator	Sterilization Method	Principle	Device	Parameter monitored
Physical	Gaseous	Temperature recording charts	Temperature recording charts	Temperature
Chemical	Gaseous	Reactive chemical	Indicator paper impregnated with a reactive chemical	Gas concentration, Temperature, Time
		Capillary principle	Based on the same migration along the wick principle	Gas concentration, Temperature, Time
		Temperature sensitive chemical	A temperature-sensitive white wax concealing a black marked	Temperature
Biological	Gaseous	Temperature sensitive microbes	Bacillus subtilis	D-value