Disinfection performance of ultraviolet germicidal irradiation systems for the microbial contamination on an evaporative humidifier

Abstract

Humidifiers have been used not only to maintain a comfortable indoor environment, but also to prevent respiratory diseases from worsening due to extremely low humidity. Some evaporative humidifiers (EH) that were considered to be energy efficient have been reported to have problems with microbial contamination. In this study, the microbial contaminations of an EH were verified, and both the germicidal effects and limitations of in-duct ultraviolet germicidal irradiation(ID-UVGI) systems against the contaminations were investigated. A numbers of bacteria and fungi were isolated from the surfaces and drain water of the EH, and airborne microbes that were likely dispersed from the contaminated EH were also detected. Based on the results of monitoring microbes for approximately six months for an ID-UVGI operation, it was found that microbial contamination was reduced but that microbes could still consistently be isolated from the surfaces and drain water. This was likely due to internal contamination of the EH in locations beyond the reach of the ultraviolet C-band (UVC) irradiation. Methods to overcome the limitations of this ID-UVGI system for EH disinfection are thus required.