C. for 15 sec. B. Membrane Filters. Good for heat-labile materials. But expensive, and filters will clog. C. Very flammable, must use special precautions.
Products retain residues of gases.
D. Radiation UV light. Gamma rays produce free radicals, destroy all kinds of chemicals. Not usually used as antiseptics, but good for swimming pools, hot tubs, water supplies. Not effective against endospores. But do kill vegetative bacteria and fungi, used extensively.