Regarding regulatory approval, 222nm far UV-C irradiation is already legal (in the US) to levels that probably significantly reduce transmission (8-hour limit of 479 mJ/cm2 for skin). Various people I know think that the limits should be much higher, but even irradiation at current US limits seems very valuable -- & very safe—to me.
While KrCl lamps are expensive, I think this post overstates how unviable they are. I think an interested organisation could afford to install & run a bunch of these in an office (within the legal limits) basically right now, and see benefits that are worth the cost. (Someone throwing cost numbers at me could ofc change my mind here.)
Seems like we still need to be be pushing for further regulatory changes. I saw a report from Kevin’s lab that the limit for is 478 mJ/cm^2 per 8-hour day, and that ~5 minutes of light at around 100mJ/cm^2 kills ~99% of (bacterial) pathogens, whereas ~5 minutes at closer to 10mJ/cm^2 kills ~90% of (bacterial) pathogens, which means we would need a higher limit. Alternatively, the current limits seem to show that AlN LEDs at 210nm would be allowed to be much stronger than 222nm, (around double?) which seems like a good reason to try to work on improving them, rather than pushing for 222nm LEDs—or pushing for KrBr Excimer lamps at 208nm, though I understand they have other problems and aren’t commercially viable at present.
(Also, why is UVA is considered so much safer for eyes than far-UVC? It seems from basic skimming that it causes long-term retinal damage...)
It seems to me like hospitals would be the kind of organizations that care a lot about reducing infections. Is there any analysis about what a hospital could achieve if they deployed it everywhere in reducing hospital-acquired infections?
Given the amount of money hospitals currently invest into keeping everything clean, they should be the kind of organizations that are first to adopt the technology even when it’s relatively expensive.
It seems to me like that price should still be okay for health care applications. Health care applications just need more clinical evidence. Without patent protection the manufactors of the lamps likely don’t have a good business model to pay for the lamps. Advances in lamp technology would have the nice benefit of producing a technology that can be defended with patents and thus making the business model work.
While KrCl lamps are expensive, I think this post overstates how unviable they are. I think an interested organisation could afford to install & run a bunch of these in an office (within the legal limits) basically right now, and see benefits that are worth the cost.
Well it depends how much UVC power you need. If a KrCl lamp with a bandpass filter is 2% efficient you can still run it at 500 Watts electrical and you have a 10-Watt source. 500 Watts electrical is totally feasible from standard electrical outlets (240 Volts @ 2 Amps), and electricity is cheap compared to the cost of lost productivity and the economic cost of death.
I would be interested to hear from some more qualified people on what power density you really need for it to work.
I have a couple disagreements with this:
Regarding regulatory approval, 222nm far UV-C irradiation is already legal (in the US) to levels that probably significantly reduce transmission (8-hour limit of 479 mJ/cm2 for skin). Various people I know think that the limits should be much higher, but even irradiation at current US limits seems very valuable -- & very safe—to me.
While KrCl lamps are expensive, I think this post overstates how unviable they are. I think an interested organisation could afford to install & run a bunch of these in an office (within the legal limits) basically right now, and see benefits that are worth the cost. (Someone throwing cost numbers at me could ofc change my mind here.)
I agree that the LEDs seem pretty hard.
Source for this? I see just 23 mJ/cm^2 given in this paper
That’s the old limit; it was changed last year. See e.g. this figure from Blatchley et al.
Seems like we still need to be be pushing for further regulatory changes. I saw a report from Kevin’s lab that the limit for is 478 mJ/cm^2 per 8-hour day, and that ~5 minutes of light at around 100mJ/cm^2 kills ~99% of (bacterial) pathogens, whereas ~5 minutes at closer to 10mJ/cm^2 kills ~90% of (bacterial) pathogens, which means we would need a higher limit. Alternatively, the current limits seem to show that AlN LEDs at 210nm would be allowed to be much stronger than 222nm, (around double?) which seems like a good reason to try to work on improving them, rather than pushing for 222nm LEDs—or pushing for KrBr Excimer lamps at 208nm, though I understand they have other problems and aren’t commercially viable at present.
(Also, why is UVA is considered so much safer for eyes than far-UVC? It seems from basic skimming that it causes long-term retinal damage...)
It seems to me like hospitals would be the kind of organizations that care a lot about reducing infections. Is there any analysis about what a hospital could achieve if they deployed it everywhere in reducing hospital-acquired infections?
Given the amount of money hospitals currently invest into keeping everything clean, they should be the kind of organizations that are first to adopt the technology even when it’s relatively expensive.
When Googling I found that Amazon.com doesn’t sell any of the KrCl lamps. https://www.waronflu.com/product/222-nm-krypton-chloride-krcl-40-watt-far-uvc-excimer-bulb-222nm-first-uvc-f-series-40w-far-uv-light-24v-dc/ seems to sell them directly. On aspect of the page is that they expect the lamps to work for 4000 hours. That means that you would likely have to reinstall new lamps every year which adds to costs.
It seems to me like that price should still be okay for health care applications. Health care applications just need more clinical evidence. Without patent protection the manufactors of the lamps likely don’t have a good business model to pay for the lamps. Advances in lamp technology would have the nice benefit of producing a technology that can be defended with patents and thus making the business model work.
Well it depends how much UVC power you need. If a KrCl lamp with a bandpass filter is 2% efficient you can still run it at 500 Watts electrical and you have a 10-Watt source. 500 Watts electrical is totally feasible from standard electrical outlets (240 Volts @ 2 Amps), and electricity is cheap compared to the cost of lost productivity and the economic cost of death.
I would be interested to hear from some more qualified people on what power density you really need for it to work.
It seems like a large amount of work of this post is being done by:
Maybe the experts are thinking of large-scale deployments in schools, hospitals, airports, conference centers? I feel like numbers seem important.
It’s false IMO, see my comment below.
https://www.lesswrong.com/posts/4Zjm8ycWhg6PzFwnF/far-uvc-light-update-no-leds-are-not-around-the-corner?commentId=NLHt7atxYX4Esuww5