ABSTRACT
Sterilization of apparatus and working areas involves the inactivation or physical elimination of all living cells and infective agents from the environment. Sterilization of culture media with ethylene oxide may change its composition by reaction with certain compounds. Flame sterilization is used for metal objects, such as transfer needles and tips of forceps, and glass objects, such as the lips of flasks and culture tubes, microscope slides and cover slips, and the surface of certain plastics. Gas sterilization is used on objects that cannot be sterilized by heat or liquid filtration. Filtration physically separates microorganisms, cells, and debris from liquids, but not viruses or metabolic by-products. Propylene oxide boils at 34°C and concentrations used for sterilization range between 800 and 2000 mg/1 of chamber space. It is less effective than ethylene oxide and has less penetrating power. Formaldehyde is an excellent microbicide and viricide but its use is restricted because of its pungency, poor penetration and high toxicity.
