Since UV-C light is delivered by UV-C lamps, a commonly asked question is how much UV-C power I should install in terms of UV-C watts. To answer this question, one must look at the fundamental UV-C inactivation science, i.e., dose-response of a target microbe at a given wavelength. UV dose is the amount of UV light delivered to its target, and is a product of UV intensity on the target and exposure time. Its unit is mJ/ cm2. Dose-response describes the relationship between log-reduction of a microbe and dose required and can be used to determine a dose target. Either UV intensity or the exposure time, or both can be adjusted to achieve the desired dose target. Hence, UV-C lamp power can be determined based on UV intensity required.
Dose for SARS-CoV-2, the virus causing COVID-19 pandemic: based on a recent IUVA White Paper (2021), at 254 nm, it takes approximately 2 mJ/cm2 to achieve 1 log10 reduction.