when will we have sufficiently conclusive evidence for the long term safety of far-uvc that it’s reasonable to push for its universal adoption in all public spaces without reservation? the safety issue seems like a much bigger deal than the cost issue for broad adoption; if it works safely, the economic case for installing far uvc in public spaces seems pretty solid—people being sick must be terrible for the economy! and they’re only ever going to get cheaper.
in a world where far uvc is near universally deployed, we might be able to banish the common cold or the flu to the past, in the same way that cholera is basically no longer a problem in the developed world. this seems like a pretty big deal and I’d like to know when this glorious future is coming (and whether there’s anything I can do to make it come sooner)!
(from eyeballing studies, it sounds like the cost of the cold+flu to the US economy is on the order of $100bn/yr, which passes basic Fermi estimate muster—given a $30tn/yr gdp, a few days per year of lost productivity due to cold/flu is easily hundreds of billions. even at the current price of far uvc, which is a huge overestimate of future tech at volume, the cost of disinfecting spaces is about $0.40/year/sqft (amortizing an aerolamp over its 5 year lifespan); compared to e.g $60/year/sqft land cost in San Francisco, this is a negligible amount. estimating the total number of sqft of public space in the US is kind of annoying, but here’s a Fermi estimate: there are about 100k schools in the US, and each school is about 100k sqft. and let’s say schools are about 10% of all public spaces. that pencils out to $100bn/year, implying we are already close to break even, despite the immaturity of the technology.)
It’s already safe beyond a reasonable doubt if kept above eye level (7 ft / 2.13m), since this massively cuts the dose absorbed. I think many public spaces should install uvc immediately, and if they’re not convinced yet just use removable shutters that keep it above eye level until more research is done.
is there a particular reason why above eye level matters? in addition to vertical height, do you also mean tilting it up so that the light points mostly at the ceiling? which sources should I look at to gain this confidence for myself
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.
when will we have sufficiently conclusive evidence for the long term safety of far-uvc that it’s reasonable to push for its universal adoption in all public spaces without reservation? the safety issue seems like a much bigger deal than the cost issue for broad adoption; if it works safely, the economic case for installing far uvc in public spaces seems pretty solid—people being sick must be terrible for the economy! and they’re only ever going to get cheaper.
in a world where far uvc is near universally deployed, we might be able to banish the common cold or the flu to the past, in the same way that cholera is basically no longer a problem in the developed world. this seems like a pretty big deal and I’d like to know when this glorious future is coming (and whether there’s anything I can do to make it come sooner)!
(from eyeballing studies, it sounds like the cost of the cold+flu to the US economy is on the order of $100bn/yr, which passes basic Fermi estimate muster—given a $30tn/yr gdp, a few days per year of lost productivity due to cold/flu is easily hundreds of billions. even at the current price of far uvc, which is a huge overestimate of future tech at volume, the cost of disinfecting spaces is about $0.40/year/sqft (amortizing an aerolamp over its 5 year lifespan); compared to e.g $60/year/sqft land cost in San Francisco, this is a negligible amount. estimating the total number of sqft of public space in the US is kind of annoying, but here’s a Fermi estimate: there are about 100k schools in the US, and each school is about 100k sqft. and let’s say schools are about 10% of all public spaces. that pencils out to $100bn/year, implying we are already close to break even, despite the immaturity of the technology.)
It’s already safe beyond a reasonable doubt if kept above eye level (7 ft / 2.13m), since this massively cuts the dose absorbed. I think many public spaces should install uvc immediately, and if they’re not convinced yet just use removable shutters that keep it above eye level until more research is done.
is there a particular reason why above eye level matters? in addition to vertical height, do you also mean tilting it up so that the light points mostly at the ceiling? which sources should I look at to gain this confidence for myself
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?