UV Air Cleaners and Upper-Room Air Ultraviolet Germicidal Irradiation for Controlling Airborne Bacteria and Fungal Spores

Abstract

In-room air cleaners (ACs) and upper-room air ultraviolet germicidal irradiation (UVGI) are engineering control technologies that can help reduce the concentrations of airborne bacteria and fungal spores in the indoor environment. This study investigated six different types of ACs and quantified their ability to remove and/or inactivate airborne bacteria and fungal spores. Four of the air cleaners incorporated UV lamp(s) into their flow path. In addition, the efficacy of combining ACs with upper-room air UVGI was investigated. With the ventilation system providing zero or six air changes per hour, the air cleaners were tested separately or with the upper-room air UVGI system in operation in an 87-m3 test room. Active bacteria cells and fungal spores were aerosolized into the room such that their numbers and physiologic state were comparable both with and without air cleaning and upper-room air UVGI. In addition, the disinfection performance of a UV-C lamp internal to one of the ACs was evaluated by estimating the percentage of airborne bacteria cells and fungal spores captured on the air filter medium surface that were inactivated with UV exposure. Average airborne microbial clean air delivery rates (CADRm) varied between 26-981 m3 hr-1 depending on the AC, and between 1480-2370 m3 hr-1, when using air cleaners in combination with upper-room air UVGI. Culturing, direct microscopy, and optical particle counting revealed similar CADRm. The ACs performed similarly when challenged with three different microorganisms. Testing two of the ACs showed that no additional air cleaning was provided with the operation of an internal UV-C lamp; the internal UV-C lamps, however, inactivated 75% of fungal spores and 97% of bacteria cells captured in the air filter medium within 60 min.

Why Does Rain Increase the Concentrations of Environmental Bioaerosols during Monsoon?

“…It has been recognized that UV irradiation can inactivate culturable bioaerosols (Riley et al, 1976;Peccia et al, 2001;Lin and Li, 2002;Kujundzic et al, 2006;Hwang et al, 2010) and that rainclouds can decrease UV irradiation intensity (Frederick and Snell, 1990;Calbó and González, 2005). Therefore, to test the hypothesis that the decrease of UV intensity on rainy days can explain the increase in bioaerosol concentrations, we attempted to quantify ambient UV irradiation intensities and bioaerosol concentrations in Seoul to observe the relationship between these two parameters.…”

Optical Barrier for Microbiological Control after a Sterilization Process

“…(9) UV radiation induces mutations in the pyrimidine dimers of DNA. (10) Distribution of light intensity shows that there is an even distribution of UV-C wavelengths in the front of the tank, which explains the oxidative damage in bacteria. Thus, it is possible that the air could be sterilized with total bacteria death within a margin of 15 cm of the optical barrier.…”

Application of ultraviolet light (UV) in dental medicdine

“…UV-C lamps are used in air, water purification and some etching processes. Testing two of the ACs showed that no additional air cleaning was provided with the operation of an internal UV-C lamp; the internal UV-C lamps, however, inactivated 75% of fungal spores and 97% of bacteria cells captured in the air filter medium within 60 min (9). Research on UV air disinfection continues today.…”