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Appl Environ Microbiol. 1968 March; 16(3): 490-495
Copyright © 1968 American Society for Microbiology. All Rights Reserved.

Microbiological Evaluation of a Large-Volume Air Incinerator

Industrial Health and Safety Office, Fort Detrick, Frederick, Maryland 21701

ABSTRACT

Two semiportable metal air incinerators, each with a capacity of 1,000 to 2,200 standard ft³ of air per min, were constructed to sterilize infectious aerosols created for investigative work in a microbiological laboratory. Each unit has about the same air-handling capacity as a conventional air incinerator with a brick stack but costs only about one-third as much. The units are unique in that the burner housing and combustion chamber are air-tight and utilize a portion of the contaminated air stream to support combustion of fuel oil. Operation is continuous. Aerosols of liquid and dry suspensions of Bacillus subtilis var. niger spores and dry vegetative cells of Serratia marcescens were disseminated into the two incinerators to determine the conditions required for sterilization of contaminated air. With the latter organisms (concentration 2.03 x 10⁷ cells/ft³ of air), a temperature of 525 F (274 C), measured at the firebox in front of the heat exchanger, was sufficient for sterilization. To sterilize 1.74 x 10⁷ and 1.74 x 10⁹ wet spores of B. subtilis per ft³, the required temperature ranged from 525 to 675 F (274 to 357 C) and 625 to 700 F (329 to 371 C), respectively. Air-sterilization temperature varied with each incinerator. This was because of innate differences of fabrication, different spore concentrations, and use of one or two burners With dry B. subtilis spores (1.86 x 10⁸/ft³), a temperature of 700 F was required for sterilization. With dry spores, no difference was noted in the sterilization temperature for the two incinerators.