An new mode formaldehyde gas sterilizer(SCHERZO : 40 type)usable under atmospheric pressure was developed, its sterilization effect was examined, and the following conclusions were obtained : (1) When 5 ml of an formaldehyde(CH_2O)solution(38%)was evaporated under the sterilization conditions of 4.0mg/l, 40℃, 72%RH, 4.2mg/l, 50℃, 63%RH, and 7.3mg/l, 60℃, 30%RH, B. subtilis var. globigii(spore, 10^6)killed in two hours(wrapped-bag made of plastic film and kraft paper)respectively, and sterilization was also possible under the same conditions, even when specified packing material was used. The D-value of the B. subtilis var. globigii(spore)measured at a reaction temperature of 50℃, 63%RH was 10 for CH_2O gas concentration 6.5mg/l, 7.5 for CH_2O gas 10.5mg/l. (2) An ammonia solution(5%)was used for neutralizing CH_2O, and a new neutralizing agent that was able to neutralize both CH_2O and ammonia was developed and used. As a result, complete neutralization was achieved after 60 minutes in total. (3) CH_2O has many advantages such as a powerful sterilizing action, being usable at lower temperature and humidity than those of ethylene oxide gas, no damage to apparatus, and moderate price.
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