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1766688 
Journal Article 
Monitoring ultraviolet lamps in biological safety cabinets with cultures of standard bacterial strains on TSA blood agar 
Harrington, BJ; Valigosky, M 
2007 
1 
Laboratory Medicine
ISSN: 0007-5027
EISSN: 1943-7730 
38 
3 
165-168 
WOS:000244537700017 
Background. Ultraviolet radiation is often used to decontaminate the interior surfaces of biological safety cabinets (BSCs). The Centers for Disease Control and Prevention (CDC) recommends a UV lamp intensity of 40 mu W/cm(2) at the center of the work area to, ensure surface decontamination. A commonly-used source of UVC in BSCs-the G30T8 lamp-provides approximately 125 mu W/cm(2) one meter from the lamp. However, since many BSCs have an interior height of less than one meter, UV intensities at the work surface, should be considerably higher because UV radiation follows an inverse square law. Few laboratories have the instruments necessary to measure UVC intensity. The Web site of the Atlantic Ultraviolet Corporation lists UV dosages required to kill a wide range of microorganisms. This study investigates the possibility of using readily available strains of 4 common bacteria to,monitor the output of UV lamps in BSCs. Methods. Inoculated plates with 4 bacterial strains were exposed to UV radiation in a plate carrier device exposed for different times and in different locations. in the BSC. Half the plates were covered with a strip of aluminum to serve as an unexposed growth control. Reduced UV intensities were simulated using Petri dish sleeves that provided a range of UV intensities,from 20 mu W/cm(2) to 510 mu W/cm(2). Various UV intensities were measured in different areas of the BSC, and compared-with calculated and estimated values. Various times to kill the bacteria were measured based on bacterial strain, UV intensity, exposure time, and location in the BSC. Results: In a blinded study in which the UV intensities were estimated from, the killing times of the bacteria and compared with actual measured values, 4 of the 6 measured values were in the estimated ranges, and 2 estimated ranges were slightly below the measured values. Conclusion: Our results support the hypothesis, that cultures of known bacterial strains could be used to closely estimate the UV lamp output.