A device for detecting a coating applied to a surface includes a portable housing, a light source, a light detector, and a processing unit. The light source emits a first light having a first wavelength. The coating includes a fluorophore that re-emits a second light having a second wavelength, which is different than the first wavelength, in response to excitation by the first light. The light detector receives the second light re-emitted from the coating. The processing unit is adapted to determine a re-emission intensity of the second light and to determine a coverage metric of the coating based on the re-emission intensity of the second light. The coverage metric is then used to infer the efficacy of the coating.