Evaluation and improvement of air quality in school public elevator

Public elevators are an essential requirement in modern high-rise buildings. However, the confined, crowded interior of an elevator provides an ideal breeding ground for all manners of biological aerosols. Consequently, when using an elevator at a university in Taiwan as the research target, this study performs an experimental investigation into the effectiveness of hand-sprayed gaseous chlorine dioxide as a disinfection agent. The air quality before and after disinfection is evaluated by measuring the bioaerosol concentrations of bacteria and fungi, respectively. The average background levels of bacteria and fungi before disinfection are found to be 635.7 +/- 469.6 and 1296.8 +/- 966.6 colony-forming unit (CFU)/m(3), respectively. Following disinfection, the bacteria and fungi concentrations reduced by an average of 35 and 25 %, respectively. The multivariate analysis of variance (MANOVA) results showed that the residual bacteria and fungi concentration levels were determined primarily by the number of individuals within the elevator and the elapsed time following disinfection. In general, the present results show that given a maximum of five individuals within the elevator, a disinfection schedule of once every 40 min is sufficient to reduce the bioaerosol concentrations of bacteria and fungi to the levels specified by the Taiwan Environmental Protection Agency (EPA).