Research may* indicate that the risk of indoor transmission is 19 times higher than outdoor transmission of COVID-19, at least according to “Indoor transmission of SARS-CoV-2” which studied 318 clusters of outbreaks.
That is of course great news during the spring and summer months but winter is still coming, at least on this hemisphere. So what can be done about the indoors?
Apparently, something with UV light. Not like the American President “thought” but rather with Far UVC light in fixtures:
Far UVC light lacks the ability to damage humans or animals, but can and will damage air- or spreadborne bacteria and viruses in short time. Installed along with ordinary light fixtures, the idea is that a very large portion of the coronaviruses will be killed in air, before reaching another person.
Far UVC light – around 200 nm – is absorbed by the ozone layer but can fairly easily be generated indoors and in sufficient power to damage the coronaviruses beyond risk of infection.
I don’t know how powerful they will have to be or how much they will cost.
*) Research regarding COVID-19 is published and pre-published a lot faster than is common, due to the ongoing pandemic. That means that we are bound to see a lot of hypotheses that turn out to be wrong.