Ultraviolet Spectral Reflectance of Ceiling Tiles, and Implications for the Safe Use of Upper-Room Ultraviolet Germicidal Irradiation

• Published in: Photochemistry and photobiology Vol. 88; no. 6; pp. 1480 - 1488
• Main Authors: Wengraitis, Stephen, Reed, Nicholas G.
• Format: Journal Article
• Language: English
• Published: Oxford, UK Blackwell Publishing Ltd 01.11.2012
• Subjects: Air Microbiology; Bacterial infections; Construction Materials; Disease prevention; Humans; Lamps; Photobiology; Spectrum analysis; Ultraviolet radiation; Ultraviolet Rays - adverse effects
• ISSN: 0031-8655; 1751-1097
• DOI: 10.1111/j.1751-1097.2012.01193.x

Ultraviolet germicidal irradiation can be used to prevent airborne transmission of infectious diseases. A common application is to irradiate upper‐room areas, by passing air from the lower room into the irradiated zone. Well‐designed systems do not expose people directly; however, some UV radiation may be reflected off ceiling tiles and wall paints into the lower room. Lower room exposure should be limited to the American Conference of Governmental Industrial Hygienists threshold limit value of 6 mJ·cm−2 of 254 nm radiation per day. To limit the lower room exposure, the reflectance of upper‐room surfaces must not be high. The reflective properties of wall paints have been studied, but less is known about the UV reflectance of ceiling tiles. Using a double monochromator spectroradiometer and an integrating sphere reflectance attachment, the UV spectral reflectance of 37 ceiling tiles was measured from 200 to 400 nm. The reflectances varied from 0.020 to 0.822 in this range, and from 0.035 to 0.459 at 254 nm, the main wavelength emitted by upper room low‐pressure mercury germicidal lamps. These data were then used to estimate an 8 h exposure based on several simplified workplace scenarios. The implications for workplace safety are then discussed. Ultraviolet germicidal irradiation (UVGI) lamps can be used to disinfect the air against viruses and bacteria. UV reflections from wall paints and ceiling tiles may be a concern for people in lower rooms. The reflective properties of wall paints have been studied, but not ceiling tiles. In our study, we measured the reflectance properties of ceiling tiles. We then estimated the lower‐room irradiances that would be incident upon the occupants in various locations of a sample room, using our measurements and data obtained from other sources.