The germicidal effects of microwave heating on microbes on evaporative humidifier elements

Abstract

To identify the germicidal effects of microwave radiation for evaporative humidifiers, we measured the germicidal effects of fungal spores of Fusarium solani and vegetative cells and spores of the bacterium Bacillus subtilis using a mock-up system. The germicidal effect was compared to the output powers, irradiation times, and water contents of the element to establish effective disinfection conditions of humidifier element surfaces. The results demonstrated that the fungal and bacterial strains were inhibited at 1200 W for 20 min, except for the B. subtilis spores under the nonoperation condition involving water spray and the blower. In general, the germicidal effects appear to be stronger on the upper portion of the elements than on the lower portion. The germicidal effect was stronger at higher output power and longer exposure time under wet conditions. To achieve a uniform disinfection on the element faces, it is necessary to consider variations of these methods to produce a uniform heating pattern.