Far-UVC (also far-UV or far-UV-C) is light with a wavelength of 200–235 nm. It is a type of germicidal ultraviolet (GUV) light, which includes the whole UVC and parts of the UVB spectrum. Far-UVC has emerged as a highly promising approach to indoor air disinfection, offering enhanced effectiveness and safety compared to conventional 254 nm upper-room GUV systems.

Resources

Blatchley, E. R., III, Brenner, D. J., Claus, H., Cowan, T. E., Linden, K. G., Liu, Y., … Sliney, D. H. (2022) Far UV-C radiation: An emerging tool for pandemic control, Critical Reviews in Environmental Science and Technology, vol. 53, no. 6, pp. 733–753.

Davidmanheim (2022) Far-UVC Light Update: No, LEDs are not around the corner, LessWrong, November 2. Linkpost from X (formerly Twitter) 

Sikes, Kirby (2020) Far-Ultraviolet Light in Public Spaces to Fight Pandemic is a Good Idea but Premature, LessWrong, April 15.