https://www.youtube.com/watch?v=U4a_kJkVUis
Big Clive’s video description:
This is not a sponsored video. I feel it’s important that people should know about this evolving technology, and Naomi is working on making it affordable.
During the pandemic YouTuber Naomi Wu presented plans for traditional mercury vapour based UVC sterilising lights with a special housing, to sterilise air in a room without exposing the occupants to the 254nm UVC light.
With the evolution and availability of the new era 222nm excimer lamps, Naomi has gone on to design a full product designed to be easy and convenient to deploy in populated areas like medical practices, waiting rooms, retail environments, food preparation areas and live events.
The special feature of the 222nm wavelength is that it is long enough to deactivate viral and bacterial air contaminants, but short enough not to pass through the outer layer of dead skin or the tear-layer of humans. That means that it is currently considered safe to use in occupied areas.
The filter on the front of the light seems to specifically pass 222nm. Without it there is a very slight hump in the spectral output at around 237nm. The filter attenuates that completely.
Excimer is an abbreviation of Excited-Dimer, where a dimer is the joining of two molecules. In the case of the excimer lamps the molecules are encouraged to bond temporarily in a plasma discharge, and when they revert back to their non-excited state they emit a photon of light at a specific wavelength determined by the chemistry. In this case it’s molecules of Krypton and Chlorine that form brief molecules of Krypton-Chloride (KrCl), before reverting back and emitting 222nm photons in the process.
The process of creating the plasma is very similar to dielectric barrier ozone generators. By coupling to the gasses capacitively the lamp also avoids contaminating the gasses with the electrode materials.
Note that the unit uses 500mA at 12V (6W) but has a generously rated 12W power supply that runs cool.
This technology looks like it may be valuable in medical, care, travel or social environments to limit the spread of pathogens.
Here’s a link to Naomi’s pleasingly-named online shop:- https://cybernightmarket.com/products
Most of the power in welding doesn’t go into UV generation, but this lamp is all about the radiation. I’d like to see a comparison of their respective UV outputs to be sure.
It is 6w before power supply losses and then a tube that is likely under 20% efficient. The primary thing that gets you with welding is the fraction of a second before an auto darkening lens activates. It is a tiny amount of time, but it adds up. Or all those times you accidentally touch the tungsten to the pool with tig. Welding has a wide spectrum, but it is the power that matters most here. The frequency and power are two separate and unrelated things. Like your microwave and WiFi are both 2.4 GHz machines. Your WiFi in your home router is limited to 100 milliwatts and is totally harmless. Your microwave needs a Faraday cage built in to avoid cooking you from the inside out because it is likely around 1500 watts. At 220nm the frequency doesn’t pass through skin or eye fluid and the power output of the light is low. Seriously, try getting into things like telescope filters where you’re trying to isolate certain frequencies. It is challenging at these frequencies to find anything that is transparent. Of all of my science books, my optics handbook is by far the largest and hardest for me to follow. That isn’t saying much, but I have built my own telescope electronics and eyepieces, along with hobby electronics, designing and etching circuit boards and photolithography using various UV lights I have built. Six watts is nothing major. I would be more concerned about how limited of an area one light can cover.
A 6W laser could easily damage the retina.
I’m not interested in rhetorical arguments guessing ‘it should be fine’. I want a radiation output comparison between this lamp and other common avenues of UV exposure (sunlight, welding, tanning beds, etc…), or the creators/relevant 3rd party safety board flat out declare the possibility of eye damage was considered/tested and ruled out.
As it stands now, the article conspicuously avoids mentioning eyes to talk about how safe the skin is and that makes me wary.