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

Yi Yang, Huihui Zhang, Sunday Segbenu Nunayon, Vincent Chan, Alvin C.K. Lai

Research output: Contribution to journalArticlepeer-review

51 Scopus citations


A full-scale ventilation duct ultraviolet germicidal irradiation (in-duct UVGI) system was designed to investigate its disinfection efficacy on five airborne pathogens: Serratia marcescens, Pseudomonas alcaligenes, Escherichia coli, Salmonella enterica, and Staphylococcus epidermidis, with airflow Reynolds numbers from 4 × 104 to 8 × 104. By varying the UV intensity, the susceptibility constants (Z-values) of the bacteria were experimentally determined to be 1.2, 1.0, 0.60, 0.39, and 0.37 m2/J for S. marcescens, P. alcaligenes, E. coli, S. enterica, and S. epidermidis, respectively. The disinfection efficacy was numerically investigated on the basis of the predicted irradiance, which included emissive irradiance and diffuse refection irradiance. The results suggest that it is vital to properly evaluate the UV dose (irradiance intensity) received by airborne bacteria to determine their Z-values. In-duct UVGI inactivated nearly all of the test bacteria with Reynolds numbers of 4 × 104 (inlet velocity = 3 m/s), and the disinfection efficacy decreased as Reynolds numbers increased. The in-duct UVGI system would potentially provide a supplementary solution for improving indoor air quality (IAQ) within mechanical ventilated/air-conditioned environment.

Original languageBritish English
Pages (from-to)806-817
Number of pages12
JournalIndoor Air
Issue number6
StatePublished - Nov 2018


  • air disinfection
  • bacteria susceptibility
  • in-duct UVGI
  • indoor air quality
  • irradiance
  • UV dose


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