* There are a sizable number of fake ones out there.
* There aren't standards and inspection tools for this.
A useful tool would be a UV detector on a stick. You touch it to the ceiling, and it reports on whether there's enough UV in the right wavelengths to kill viruses. The idea is to have emitters which radiate horizontally, with most of the UV up near the ceiling.
You also need a handheld device which checks at eye level for excessive near UV. With both of those, you could quickly tell if a room had reliable virus protection.
All that makes sense - for an ordinary product in an ordinary market.
But this seems like something that could make a serious dent in the covid situation and so government mandates and money could flow and get these much more widely deployed with strong standards.
Also possibly useful military applications. Heck, have the soldiers wear some goggles that have UV protection and just saturate the room in virus killing UV periodically if there’s a suspected biological attack.
Although, why not just put this UV emitter in a big box that has some kind of light filter on it to keep the UV inside rather than worrying about top of the room and so on?
Because you have to push the air through the box with fans. If you can make the ceiling area a kill zone for viruses, ordinary convection effects will push all the air through it regularly.
Also, the UV light involved is very damaging to eyes (causing cataracts and macular degeneration), so it has to be kept entirely contained, yet have all/most of your breathable air pass through it somehow.
They make these for hvac systems, mines installed in the air return, fully enclosed it works well. When the heat or AC isn't in use, I just run the hvac system fan.
* The far-UV lamps cost way too much.
* There are a sizable number of fake ones out there.
* There aren't standards and inspection tools for this.
A useful tool would be a UV detector on a stick. You touch it to the ceiling, and it reports on whether there's enough UV in the right wavelengths to kill viruses. The idea is to have emitters which radiate horizontally, with most of the UV up near the ceiling. You also need a handheld device which checks at eye level for excessive near UV. With both of those, you could quickly tell if a room had reliable virus protection.