Hi, I stumbled upon this website and threads, and even if I'm not an expert (just a EE), I researched a little on this topic to choose a disinfection device and policy to use when entering home during this emergency and for reusing masks by disinfecting them, too (due to no availability here in Italy) .My best findings follow.
You can find all needed numbers (fluence (technical name for "dose") for disinfecting virus by UVC irradiation, or UVGI -Ultraviolet Germicidal Irradiation- as its known ) here:
https://www.nrcresearchpress.com/doi/ab ... oM_6c2xU-W
https://oeh.tandfonline.com/doi/full/10 ... laBb80o8-V
Behind paywall there is an introduction to air disinfection by UV-C here: https://www.atsjournals.org/doi/abs/10. ... lCode=arrd
Just to recap, a fluence of more than 50 mJ/cm2 (at 254 nm) is recommended by regulating bodies for disinfection of water, the same value is shown by clinical studies to be a well reasoned number for RNA viruses in air, too (for covid-19 and all coronaviruses -RNA based-, allow 4 log 10 abatement, that means 10,000 times less (source: http://www.iuva.org/UV-FAQs ), according with chick's law N = No e^(-kIt) that describe survivors after a given irradiance I and time t of a given population No ).
Due to the fact that fluence is function of time of esposition (J=W s), a suitable irradiated path length can be calculated for any UVC source and air velocity. Of course, to avoid eye and skin harm, UV-C exposure of living being must be avoided.
Another very interesting proposal is by Irving Medical Center of Columbia University. They found that 220 nm UVC are safe to eye and skin, thus proposed recently they can be used to avoid flu spreading, by disinfecting air, in this case just mounting 220 nm lamps in clear view together with common lighting lamps. At best of my knowledge this technology is not commercially available, though. And I'm not aware of any other clinical or peer reviewed study to determine needed fluence (changing wavelength change absorbance by virus's DNA/RNA -maximum is around 260 nm- and thus a new dose (fluence) must be determined to obtain the abatement requested). Their paper give number here: https://www.nature.com/articles/s41598-018-21058-w while a layman introduction is here: https://www.cuimc.columbia.edu/news/can ... -influenza
Speaking of practical implementation, common fluorescent-type lamps are commercially available by many sources. I found Philips (https://www.lighting.philips.com/main/p ... rification their catalogue here: https://www.sillamps.com/custom/www.sil ... m_sl_3.pdf ) and OSRAM PURITEC (brochure here: http://dammedia.osram.info/media/resour ... 20(EN).pdf ) the nearest suppliers (and most spread: quick availability was a key in my research). Same ballast of common equivalent fluorescent lamps can be used.
LED sources around 260 nm exist, too. Tough they can be more apt for a project like this due to small dimensions (and duty cycle), I have not researched this solution, thus I cannot suggest any. However, I know Philips NaturalTrust (https://www.assets.signify.com/is/conte ... eneral.pdf ) and Klaran (https://www.klaran.com/ ) have an offer of UVC LED for germicidal application.
Hope this can help.