Pointing UVC LEDs at your ceiling seems sketchy. White paint will likely scatter ~5% of UVC, and shiny metal surfaces will scatter more. Try to go below 250nm for reduced reflection (and reduced penetration into human skin) and (more) unwanted chemistry will start happening to the air.
I guess an important question is whether UVC is more harmful than UVB. If it’s not any more harmful, then as long as nobody’s getting sunburned from being in that room all day, it’s probably fine—that 5% scattering is just another name for SPF 20. But if it is more harmful, then sunburn might not be an adequate signal for when it’s bad for you.
You do need to pay attention to what paint is on the ceiling and measure to verify that levels are low in the places people are, but pointing UVC up is something we’ve done safely for a long time in many places.
If you want to do this as a successful company, you essentially have to get your customers to trust you that you are installing it in a way where UVC up does not produce any negative effects.
People have been doing it for decades is not something that would convince me that there are not long-term side-effects.
The way you demonstrate that there are not long-term side effects is that we have very accurate ability to measure UV, and so you can show that the system being on vs off has a negligible impact on the amount of UV where people are. Long-term impacts would be downstream from this kind of easily detectable effect.
(I think this is very different for far UV, where you intentionally shine it in a way that does include the people. That is potentially a much better approach, because you can clean the air between people instead of only above them, but while the research on far UVC safety looks pretty good to me, it’s a much harder system to gather safety evidence on.)
Pointing UVC LEDs at your ceiling seems sketchy. White paint will likely scatter ~5% of UVC, and shiny metal surfaces will scatter more. Try to go below 250nm for reduced reflection (and reduced penetration into human skin) and (more) unwanted chemistry will start happening to the air.
I guess an important question is whether UVC is more harmful than UVB. If it’s not any more harmful, then as long as nobody’s getting sunburned from being in that room all day, it’s probably fine—that 5% scattering is just another name for SPF 20. But if it is more harmful, then sunburn might not be an adequate signal for when it’s bad for you.
You do need to pay attention to what paint is on the ceiling and measure to verify that levels are low in the places people are, but pointing UVC up is something we’ve done safely for a long time in many places.
If you want to do this as a successful company, you essentially have to get your customers to trust you that you are installing it in a way where UVC up does not produce any negative effects.
People have been doing it for decades is not something that would convince me that there are not long-term side-effects.
The way you demonstrate that there are not long-term side effects is that we have very accurate ability to measure UV, and so you can show that the system being on vs off has a negligible impact on the amount of UV where people are. Long-term impacts would be downstream from this kind of easily detectable effect.
(I think this is very different for far UV, where you intentionally shine it in a way that does include the people. That is potentially a much better approach, because you can clean the air between people instead of only above them, but while the research on far UVC safety looks pretty good to me, it’s a much harder system to gather safety evidence on.)