Thread by @joeyfox85

Purchasing a Far-UV Lamp

Here's a review of what I know about the Far-UV market and what you can consider when purchasing a lamp.🧵

First, I'm hesitant to post this as I have not done extensive research into every possible option that exists and this will open me up to a lot of criticism (I've avoided a lot of tweets for this reason), but no one else is offering guidance. This is what I know.

There are 5 main sources I know of: Ushio, Ergo Health, UV Can Sanitize/ First UVC, Sterilray, Eden Park.

Ushio produces filtered lamps, I think they are the most common. Usually around 15 W. Here's a long list of companies that sell them:
care222.com/care222-partne…

Ergo Health sells the X-One. We don't have evidence that a 3 W lamp would be effective in any setting. I'm skeptical and wouldn't use it until there is more evidence.
ergo-healthtech.com/xone

UV Can Sanitize and First UVC sell the same products (one in Canada and one in the US). These products are filtered and appear to be much cheaper than the Ushio products.

uv-can.com/collections/fa…
firstuvc.com

Sterilray produces unfiltered lamps. They are powerful and have a longer life than other lamps. See below on advice for safe use.
sterilray.com

Eden park produces filtered lamps. It looks like they have the best portable device available - 10 W.

edenpark.com/products/mobil…

Cost

I've seen Ushio and Sterilray prices around $2-$4 k USD.
X-One is $343 USD
UV Can Sanitize has prices around $800-1500 CAD (600-1200 USD). Not sure about First UVC.
Don't know about Eden Park's prices.

Power - You need to find the balance between safe (staying below the limits) and effective. 15 W is likely to be effective in a small room (like in your home). Higher power is more effective. Once power is too low, it's ineffective. It doesn't necessarily scale linearly.

Rough dosing formula:
15 W in a room 32 m^3 = 33-66 ACH.

They didn't use respiratory aerosols and used bacteria that are harder to inactivate than COVID. Very rough estimate for real life, but it's the best we got right now.

nature.com/articles/s4159…

Safe Use
You need to know the irradiation at different distances. Dose limits for filtered far-uv are:
Eyes - 160 mJ/cm²
Skin - 479 mJ/cm²

Find out the irradiance at different distances and multiply by time.

UV Medico (they sell Ushio) has a really helpful graph. For a 17 W, 100 deg, 1 m distance, the irradiance is 3.2 µW/cm².

Dose = irradiance x time
Eye dose (160 mJ/cm²)/irradiance (3.2 µW/cm²) x 1000 = 50000 seconds = 14 hours /day.

uvmedico.com/lamps/uv222-sp…

So there's no concern staring at a 15 W, 100deg lamp from 1 m away for a long period. Different wavelengths have different limits and different power lamps have different irradiances. I have no concern about safe use of 15 W filtered lamps unless holding it very close for hours.

I also have this data for the 60 deg lamps. They are sold as Delphi by UV Can Sanitize and DF-28B by First UVC.
Staring at a 20 W lamp from 1 m:
160 mJ/cm²/22 µW/cm² x 1000 = 7272 seconds = 2 hours

If you want to buy Sterilray, here's my advice.
Speak with the manufacturer and find out the irradiances at different wavelengths and different distances. Find out the limits at the different wavelengths and ensure you are using it in a way to remain below the limits.

I've purchased from UV Can as they seem to be the only ones in Canada. I've purchased the Lily, it's 2 W and unlikely to be effective. I've purchased the carnation which is 15 W. It's likely to be effective, but I have electrical safety concerns.

It's high voltage exposed wiring, so speak with the seller before you purchase. Other lamps are better from an electrical safety perspective. The prices from them seem to be substantially lower than the other ones I've seen in the US.