45 Biosafety Manual is brown or yellow, it is active. Sodium thiosulfate solution can be used to readily inactivate iodophors and remove iodophor stains. • Peracetic acid – used most commonly to sterilize gnotobiotic animal-holding chambers and equipment ¤ Peracetic acid is effective against bacteria, viruses, fungi, and bacterial spores. It is very powerful and fast-acting. ¤ Effective concentration is 2% in water, or 0.08% solution in 10-20% ethanol. The ethanol solution has fewer adverse properties than the 2% solution in water. ¤ Peracetic acid is received as a 40% concentrated solution, which can explode if contaminated with heavy metals or reducing agents, or if rapidly heated. It is also flammable and must be refrigerated. It is a potent respiratory irritant and requires a respirator for use. Peracetic acid is corrosive to metal surfaces. ¤ Diluted solution degrades rapidly, so it must be freshly prepared for use. • Phenolic compounds (for example, Amphyl, Vesphene II) – commonly used for disinfecting contaminated walls, floors and bench tops ¤ Phenolic compounds are effective against vegetative bacteria, including mycobacterium tuberculosis, fungi, and lipophilic viruses. They are not effective against spores and non-lipid viruses. ¤ Effective concentrations are 0.5-2.0%. ¤ Phenolic compounds produce an unpleasant odor and are toxic. ¤ These are irritants to the eyes, skin, respiratory tract, and gastric tract. • Quaternary Ammonium compounds – cationic detergent (surfactant) with strong surface activity, commonly referred to as “Quats” ¤ Quats are effective against fungi, Gram-positive bacteria, and lipophilic viruses, but less effective against Gramnegative bacteria. They are ineffective against hydrophilic viruses or bacterial spores. Quats mixed with phenolics are very effective disinfectants, as well as cleaners. ¤ Usual effective concentration is 1:750. ¤ These are relatively nontoxic and acceptable as a general disinfectant, such as for decontaminating food equipment or for general cleaning.