Thread by @ellakahl

Good article for anyone freaking out about the dangers of Far-UV tech. Covid, not surprisingly, is FAR more dangerous. The dangers of Far-UV at 222-nm are basically nonexistent. It's an expensive but viable way to protect oneself in the plague infested waters we are all wading through.

"Comparing this typical spectrum of an unfiltered KrCl lamp with the oxygen absorption of Fig. 1, one will find that there is an insignificant, but detectable amount of radiation below 200 nm that can produce ozone. That means that there is a potential that ozone can be generated by this kind of lamp. However, the contribution of the main 222-nm wavelength to the ozone generation is usually negligible."

Further "It should be noted that the spectrum is inherent to all KrCl discharge lamps, so it typically does not depend on the manufacturer, lamp design or the applied technology. Some manufacturers have developed sophisticated filter technology to not only suppress radiation above 230 nm but also apply filter technology to reduce wavelengths below 200 nm and therefore further reduce ozone generation."

Another article on recent safety testing in California of UV over 200-nm: ledsmagazine.com/lighting-healt…

"UV-C is the shortest wavelength band of ultraviolet radiation, ranging from 100–280 nm. It has been proven at certain wavelengths and doses to kill SARS-CoV-2. Products have emerged at 222, 254, and 265 nm. In a webcast presentation with LEDs Magazine last summer, Robert Karlicek, director of the Center for Lighting Enabled Systems & Applications (LESA) at Rensselaer Polytechnic Institute, noted that “ozone production is significant only below 200 nm.”

A good thread on far-UV from my friend @Michael59503746

https://twitter.com/Michael59503746/status/1715347894071353817

Another peer reviewed article from The Royal Society of Chemistry:
pubs.rsc.org/en/content/art…

"At a 222 nm UV dose of 50 mJ cm−2, the increase in indoor endotoxin activity due to illuminated GNB in typical indoor environments was estimated to be 3 orders of magnitude lower than the pre-existing endotoxin activity. Thus, our work suggests a negligible increase in endotoxic risk due to 222 nm indoor disinfection."

One more: chemrxiv.org/engage/api-gat…

"GUV222 may be effectively used in conjunction with ventilation: relatively modest irradiation
levels combined with carefully chosen ventilation conditions can greatly enhance the effective
air change rate (Figure 5A), while limiting the levels of secondary pollutants"

And to be noted, many manufacturers of current Far UV devices incorporate safety measures to prevent or minimize ozone release.

Another: tandfonline.com/doi/full/10.10…

"Ozone production from KrCl* lamps is modest, such that control of indoor ozone from these systems can be accomplished easily using conventional ventilation systems. This set of characteristics offers the potential for Far UV-C devices to be used in occupied spaces, thereby allowing for improved effectiveness for inactivation of airborne pathogens, including those that are responsible for COVID-19."

One can also research manufacturers. Some have patented tech for added safety. For example the Sterilray Light Sabre says it is ozone free. sterilray.com/sterilray/prod…

"Dry, Chemical Free – environmentally friendly, will not harm interior surfaces, lamps produce no ozone." My guess is they preprinted the electrodes directly on the glass, encased the whole bulb in ozone - reduction material or applied a filter.