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You can get 265-275nm LEDs- they are effective but you have to check them since there are constant scams.

https://twitter.com/RealSexyCyborg/status/154177301370350387...

You also have to dump a lot of heat so there's fan noise and Upper-Room GUV is already quite cheap so they aren't really game changers in that application- but they do work.

https://twitter.com/RealSexyCyborg/status/153744305018765722... https://twitter.com/RealSexyCyborg/status/153944537069847756...

222nm excimer lights are pretty costly per joule compared to 254-275nm given the 3,000hr or so lifespan of typical Chinese bulbs (although USHIO claims 10,000 is on the way) but from working with the factories they aren't quite as expensive as people think- the distributor markup is huge. You can also squeeze about 30% more out of them by switching to PTFE reflectors:

https://twitter.com/RealSexyCyborg/status/156236957519840051...

Best would be no reflector at all and pump as many joules into room air as we can with some air circulation, but right now we can only do that with unfiltered excimer lights- which aren't horrible but not something you'd want to sit with for several hours a day:

https://twitter.com/RealSexyCyborg/status/157656585826391244... https://twitter.com/RealSexyCyborg/status/159832965174278963...

Cylindrical 222nm cut filters would solve this but so far we can only get flat panes- and they are quite costly so building a square or triangular enclosure of filters costs more than you gain.

For what it's worth I make pretty extensive use of (filtered) 222nm- both portable and at home and I haven't caught COVID yet. Just an anecdote, but I've got no reason to stop using it- at least personally.

https://twitter.com/RealSexyCyborg/status/159942679977541222... https://twitter.com/RealSexyCyborg/status/159708372174773452... https://twitter.com/RealSexyCyborg/status/158850109792860160... https://twitter.com/RealSexyCyborg/status/161091221064529920...

The math on wearable Far-UVC didn't work out (exposure time is too short for the power, high power exceeds the TLV at that distance)- but it was a fun side project for a couple of days:

https://twitter.com/RealSexyCyborg/status/157297688745831219... https://twitter.com/RealSexyCyborg/status/158296013877611315...

As far as 222nm safety, I'm comfortable with it based on current data, used within recommended TLVs and have tested it on myself at length. But the one area I have concerns is folks with Lupus and other UV-sensitive immune disorders. It should be ok given that UVB seems to be the problem region, but we really have no information and I'd like some before any real widespread roll out of this technology.

https://twitter.com/RealSexyCyborg/status/155949983593741926...

discuss

Animats|3 years ago

> but from working with the factories they aren't quite as expensive as people think- the distributor markup is huge.

That is good to know. In the US these things are sold by high-markup "lifestyle" suppliers. Gas-discharge tubes are not inherently expensive, but the market is not yet large.

> A visible light filter that allows 222nm through. ... No blue UV death glow...

Yes. For long-term deployment that's needed.