October 3, 2022

Reflectance measurements of building materials in the far UVC (222 nm) wavelength range


Recently the application of far ultraviolet (UVC 200-230nm) optical radiation for disinfection of occupied spaces has seen a growing interest. Filtered excimer krypton-chloride (KrCl) lamps, which emit predominantly at 222 nm, have been shown to provide similar or better pathogen reduction rates, while being safe for human eye and skin exposure at much higher dose levels than the typical 254 nm radiation. This opens new opportunities to provide disinfection of air and surfaces while people are present. The installations of 222 nm light fixtures are professional planned using adopted light planning software. In order to achieve reasonable accurate radiation distribution models and predict the applied UV dose levels, the reflectance of the materials found in the space needs to be considered. Unfortunately, there is very little literature on the reflectance of interior building materials in UV. The paper presents a simplified setup for collecting reflectance data, using an existing polytetrafluoroethylene (PTFE) sphere, a 222 nm radiometer, and a filtered excimer KrCl lamp. Common building materials have been investigated with this method and most of them showed a diffuse reflectance of about 10%. Reflectance measurements were also made by the National Institute for Standards and Technology (NIST) for the purpose of validating the method. Advantages and disadvantages of the applied method are discussed.

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