Effects of ultraviolet germicidal irradiation and swirling motion on airborne Staphylococcus aureus, Pseudomonas aeruginosa and Legionella pneumophila under various relative humidities
Article first published online: 10 JUL 2012
© 2012 John Wiley & Sons A/S
Volume 23, Issue 1, pages 74–84, February 2013
How to Cite
Chang, C.-W., Li, S.-Y., Huang, S.-H., Huang, C.-K., Chen, Y.-Y. and Chen, C.-C. (2013), Effects of ultraviolet germicidal irradiation and swirling motion on airborne Staphylococcus aureus, Pseudomonas aeruginosa and Legionella pneumophila under various relative humidities. Indoor Air, 23: 74–84. doi: 10.1111/j.1600-0668.2012.00793.x
- Issue published online: 9 JAN 2013
- Article first published online: 10 JUL 2012
- Accepted manuscript online: 8 JUN 2012 03:36PM EST
- Received for review 15 November 2011. Accepted for publication 19 May 2012.
- Staphylococcus aureus;
- Pseudomonas aeruginosa;
- Legionella pneumophila;
- ultraviolet germicidal irradiation;
- swirling motion;
- relative humidity
Abstract Staphylococcus aureus, Pseudomonas aeruginosa, and Legionella pneumophila have been detected in indoor air and linked to human infection. It is essential to adopt control methods to inactivate airborne pathogens. By passing bioaerosols horizontally into a UV device at two flow rates (Qs) and moving cells around a central UVC lamp at relative humidity (RH) of 12.7–16.7%, 58.7–59.6%, and 87.3–90%, the effects of swirling motion and 254-nm ultraviolet germicidal irradiation (UVGI) against bioaerosols were assessed under UV-off and UV-on settings, respectively. An inverse relationship between RH and UVGI effectiveness was observed for every test bioaerosol (r = −0.74 ∼ −0.81, P < 0.0001). Increased UV resistance with RH is likely associated with the hygroscopicity of bioaerosols, evident by increased aerodynamic diameters at high RH (P < 0.05). UVGI effectiveness was significantly increased with decreasing Q (P < 0.0001). Moreover, P. aeruginosa was the most susceptible to UVGI, while the greatest UV resistance occurred in L. pneumophila at low RH and S. aureus at medium and high RH (P < 0.05). Results of UV off show P. aeruginosa and L. pneumophila were more sensitive to air-swirling motion than S. aureus (P < 0.05). Overall, test bioaerosols were reduced by 1.7–4.9 and 0.2–1.7 log units because of the UVGI and swirling movement, respectively.
The studied UV device, with a combination of swirling motion and UVGI, is effective to inactivate airborne S. aureus, P. aeruginosa, and L. pneumophila. This study also explores the factors governing the UVGI and swirling motion against infectious bioaerosols. With understanding the environmental and operational parameters, the studied UV device has the potential to be installed indoors where people are simultaneously present, for example, hospital wards and nursing homes, to prevent the humans from acquiring infectious diseases.