Disinfection by in‐duct ultraviolet lamps under different environmental conditions in turbulent airflows

Abstract

In this study, we investigated the effects of environmental factors such as airflow velocity, relative humidity (RH), temperature, and duct reflectance on the performance of in‐duct UVC lamps. Staphylococcus epidermidis, Pseudomonas alcaligenes, and Escherichia coli were used as the test bacteria. The UV irradiance, disinfection efficacy, and UV susceptibility constant (Z value) of the test bacteria were experimentally determined. The results showed that the UV disinfection efficacy decreased as the airflow velocity and RH increased. The maximum UV disinfection efficacy was obtained at temperature of 20‐21°C compared with the performance at lower temperature (15‐16°C) and higher temperature (25‐26°C). When the RH increased from 50% to 90%, the Z values of airborne bacteria reduced by 40%, 60%, and 38% for S epidermidis, P alcaligenes, and E coli, respectively. Besides, susceptibility constants had lower values under both cooling temperature (15‐16°C) and heating temperature (25‐26°C) compared with that under the temperature of 20‐21°C. It was observed that S epidermidis generally had the highest resistance to the UV irradiance. The results also showed that the UV disinfection efficacy was lower in the duct with a black surface than in the clean duct.

Indoor Air Quality Strategies for Air-Conditioning and Ventilation Systems with the Spread of the Global Coronavirus (COVID-19) Epidemic: Improvements and Recommendations

“…Zhang et al [ 132 ] have studied the factors that affect the performance of UVC lamps installed in the duct as a means of killing bacteria and viruses. They included airflow velocity, relative humidity (RH), temperature, and duct reflectance.…”

Perspectives on UVC LED: Its Progress and Application

“…Regarding the flow rate, environmental factors such as temperature, humidity, and pipe reflectivity have an impact on the UVC lamp with sensor. Performance impact studies have also shown that with an increase in air velocity and relative humidity, the bactericidal effect decreases to a certain extent [103]. Comparison of UVC to performance ratio at low (15-16 • C) and higher temperatures (25-26 • C) reveal that UVC has a maximum sterilization effect at a temperature of 20-21 • C.…”

Spatial analysis of the impact of UVGI technology in occupied rooms using ray‐tracing simulation

“…Harvard School of Public Health's past research on UVGI technology by First et al 9,16,17 has provided guidelines that mainly focus on the microorganism inactivation potential of this technology. Other studies have examined the disinfection efficacy of in‐duct UVGI system 18,19 . Here we focus on the impact of room design on the effectiveness of upper‐room UVGI and the safety of the lower zone of the room.…”