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J Appl Microbiol. 2008 Feb;104(2):489-98. Epub 2007 Oct 9.

The inactivation and removal of airborne Bacillus atrophaeus endospores from air circulation systems using UVC and HEPA filters.

Author information

1
Center for Biological Defense, College of Public Health, University of South Florida, Tampa, FL 33612, USA. vluna@health.usf.edu

Abstract

AIMS:

To (i) evaluate the UV radiation in the 'C' band/high efficient particulate air (UVC/HEPA) instrument's potential to inactivate spores of Bacillus atrophaeus and selected Bacillus species and (ii) test whether a titanium dioxide coating inside the cylindrical HEPA filter improves the system's efficacy.

METHODS AND RESULTS:

Known amounts of dried spore preparations of B. atrophaeus, Bacillus cereus, Bacillus megaterium, Bacillus stearothermophilus and Bacillus thuringiensis were exposed to the UVC lamp within a cylindrical HEPA filter for different time lengths (30 min to 48 h) and with different air flow speeds (0-235 l s(-1)). The log(10) reduction (range 5-16 logs) of colony forming units for spores exposed to the UVC compared with the unexposed spores was significant (P < 0.0001). The addition of a titanium dioxide (TiO(2)) veneer to the interior surface of the HEPA filter significantly increased the inactivation of spores (P < 0.0001).

CONCLUSIONS:

The UVC/HEPA unit could inactivate spores of B. atrophaeus, B. cereus, B. megaterium, B. stearothermophilus and B. thuringiensis.

SIGNIFICANCE AND IMPACT OF THE STUDY:

The UVC/HEPA unit represents an effective method of decontaminating circulating air within an air-duct system as found in a building.

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