Minimizing the exposure of airborne pathogens by upper-room ultraviolet germicidal irradiation: an experimental and numerical study

Abstract

There has been increasing interest in the use of upper-room ultraviolet germicidal irradiation (UVGI) because of its proven effectiveness in disinfecting airborne pathogens. An improved drift flux mathematical model is developed for optimizing the design of indoor upper-room UVGI systems by predicting the distribution and inactivation of bioaerosols in a ventilation room equipped with a UVGI system. The model takes into account several bacteria removal mechanisms such as convection, turbulent diffusion, deposition and UV inactivation. Before applying the model, the natural die-off rate and susceptibility constants of bioaerosols were measured experimentally. Two bacteria aerosols, Escherichia coli and Serratia marcescens , were tested for this purpose. It was found out that the general decay trend of the bioaerosol concentration predicted by the numerical model agrees well with the experimental measurements. The modelling results agree better with experimental observations for the case when the UVGI inactivation mechanism dominates at the upper-room region than for the case without UVGI. The numerical results also illustrate that the spatial distribution of airborne bacteria was influenced by both air-flow pattern and irradiance distribution. In addition to predicting the local variation of concentration, the model assesses the overall performance of an upper-room UVGI system. This model has great potential for optimizing the design of indoor an upper-room UVGI systems.

Disinfection efficacy of ultraviolet germicidal irradiation on airborne bacteria in ventilation ducts

“…As shown in Figure , a full‐scale ventilation duct system was built for experimental testing. This duct system has been introduced elsewhere . The air temperature and relative humidity (RH) in the duct were maintained at 23°C ± 2°C and 55% ± 5%, respectively, during the experimental procedure.…”

“…The experimental procedures for the growth and harvest of bacteria are widely reported in the literature . Briefly, bacteria stock which was stored under −80°C refrigeration was brought into a nutrient broth (NB, Oxoid) or trypticase soy broth (TSB, Oxoid).…”

“…The numerical Eulerian method, which considers the inactivation rate of UVGI as a sink term in the bacteria transport equation, has been successfully applied to study the disinfection of upper‐room UVGI . Noakes et al .…”

A pilot study on the disinfection efficacy of localized UV on the flushing-generated spread of pathogens

“…An UR-UVGI fixture with a germicidal lamp (TB-12-W, American Ultraviolet) was mounted at the center of the side wall near the outlet, at a height of 2.05 m. This fixture held a 16 W UV-C lamp. Such a system has been used in other studies [21,22]. For the localized configuration, lamps with two power levels were used: 5 W and 10 W (Philips, PL-S, TUV), each of them with a ballast housed in a water-resistant clear Perspex box.…”

A tracing method of airborne bacteria transmission across built environments

“…In CFD, the tracer gases were generally represented by passive scalars, which were just following the air movement. Particles (e.g., fluorescent particles) and some microbial surrogate were also considered as tracers to investigate the airborne transmission of microorganism [31][32][33][34][35][36][37]. DNA barcoded aerosol, as a novel test particle overcoming the effect of test material from pre-existing environmental or background contaminants, was developed to track the fate of the airborne particle in built environment [38,39].…”