TABLE 4.1 Common Sterilization Procedures

Procedure—Target

Techinique—Problems

Dry heat—exterior/interior

105-180 °C for 1 to 300 hours—Problems caused by thermomechanical incompatibility between materials can lead to the faliure of electronic components.

Wet heat—exterior/interior

120-134 °C for 3 to 20 minutes—Problems can be caused by steam (e.g., corrosion and water absorption).

Alcohol wipes—exterior surfaces

Isopropyl or ethyl alcohol swabbing—Problems arise because interior and encased surfaces (e.g., electronic components) are inaccessible.

Ethylene dioxide—exterior/internal exposed surfaces

Toxic gas, 40 to 70 °C—Problems arise because the gas can only reach exposed surfaces and because it is absorbed by some types of polymers (e.g., rubbers and polyvinyl chloride).

Gamma radiation—exterior/subsurface

Typically, 2.5 Mrad—Problems encountered include optical changes in glasses and damage to electronics and solar cells.

Beta radiation—exterior/near-surface

1 to 10 MeV—Problems arise because of limited penetration.

Hydrogen peroxide plasma—exterior/internal exposed surfaces

6 mg/l H202 concentrated at 58%—Problems can be encountered because the unexposed surfaces remain untreated.

Ultraviolet—exterior surfaces

5,000 to 20,000 J/m2—Problems arise because unexposed surfaces remain untreated.

Methyl bromide—exterior/internal exposed surfaces

Toxic gas—Problems can be encountered because unexposed surfaces remain untreated and because the gas catalyzes chemical reactions between metal and other components.

These treatments can be highly effective, but they have their limitations in certain circumstances. Important factors influencing germicidal activity include the following: the types of microorganisms; the number of organisms; the intrinsic resistance of the organisms; the amount of organic soil on the item to be sterilized; the type and concentration of germicide; the time and temperature of exposure; and the compatibility between of the device being sterilized and the technique being used.



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