The light should point mostly in a horizontal plane just below the ceiling of the room, so that no one has the light shining directly in their eyes. Here’s a source and there are more sources linked from here, including a DIY guide.
Since upper room UVGI when not filtered to 222nm is probably safe, and far-UVC which IS filtered to 222nm is probably safe even when it shines on occupants’ eyes and bodies, it stands to reason that upper-room UVC has enough safety margin. To the best of my knowledge, far-UVC has been tested up to doses equivalent to 3 years of 8h/day exposure at the current safety threshold, but eyes are delicate so I would prefer studies of 10-100x higher cumulative doses.
isn’t upper room far UVC strictly less effective than upper room normal UV, simply because of far UVC lamps being much more expensive and inefficient, and the only benefit of far uvc being that it is safe to shine directly on people? (and simply by virtue of being much better established, upper room UV seems like an easier sell to people who defer to authority for safety, even if it strictly less safe than upper room far UVC)
while we’re on the subject, how much more effective is far UVC (shone directly on people) vs upper room UV?
Plausibly yes, but I’d be worried enough about residual exposure (reflections off walls, improper installation) to other UV wavelengths that installation is likely to require some care and expense too. The second link has several accounts of acute health effects from people doing upper room UV wrong. Probably still great to have in train stations, airports etc though given the enormous benefit/cost ratio.
how much more effective is far UVC (shone directly on people) vs upper room UV?
I’m not really sure, there would be a component from surfaces and a component from extra ACH due to not relying on vertical air mixing. There are probably studies.
The light should point mostly in a horizontal plane just below the ceiling of the room, so that no one has the light shining directly in their eyes. Here’s a source and there are more sources linked from here, including a DIY guide.
Since upper room UVGI when not filtered to 222nm is probably safe, and far-UVC which IS filtered to 222nm is probably safe even when it shines on occupants’ eyes and bodies, it stands to reason that upper-room UVC has enough safety margin. To the best of my knowledge, far-UVC has been tested up to doses equivalent to 3 years of 8h/day exposure at the current safety threshold, but eyes are delicate so I would prefer studies of 10-100x higher cumulative doses.
isn’t upper room far UVC strictly less effective than upper room normal UV, simply because of far UVC lamps being much more expensive and inefficient, and the only benefit of far uvc being that it is safe to shine directly on people? (and simply by virtue of being much better established, upper room UV seems like an easier sell to people who defer to authority for safety, even if it strictly less safe than upper room far UVC)
while we’re on the subject, how much more effective is far UVC (shone directly on people) vs upper room UV?
Plausibly yes, but I’d be worried enough about residual exposure (reflections off walls, improper installation) to other UV wavelengths that installation is likely to require some care and expense too. The second link has several accounts of acute health effects from people doing upper room UV wrong. Probably still great to have in train stations, airports etc though given the enormous benefit/cost ratio.
I’m not really sure, there would be a component from surfaces and a component from extra ACH due to not relying on vertical air mixing. There are probably studies.
What about negative effects on the symbiotic microbiome?