Germicidal UV lights could be producing indoor air pollutants, study finds

Life is full of trade offs! What is worse?

From the abstract:

"One strategy for mitigating the indoor transmission of airborne pathogens, including the SARS-CoV-2 virus, is irradiation by germicidal UV light (GUV). A particularly promising approach is 222 nm light from KrCl excimer lamps (GUV222); this inactivates airborne pathogens and is thought to be relatively safe for human skin and eye exposure. However, the impact of GUV222 on the composition of indoor air has received little experimental study. Here, we conduct laboratory experiments in a 150 L Teflon chamber to examine the formation of secondary species by GUV222. We show that GUV222 generates ozone (O3) and hydroxyl radicals (OH), both of which can react with volatile organic compounds to form oxidized volatile organic compounds and secondary organic aerosol particles. Results are consistent with a box model based on the known photochemistry. We use this model to simulate GUV222 irradiation under more realistic indoor air scenarios and demonstrate that under some conditions, GUV222 irradiation can lead to levels of O3, OH, and secondary organic products that are substantially elevated relative to normal indoor conditions. The results suggest that GUV222 should be used at low intensities and in concert with ventilation, decreasing levels of airborne pathogens while mitigating the formation of air pollutants."

Germicidal UV lights could be producing indoor air pollutants, study finds | MIT News | Massachusetts Institute of Technology While useful for killing pathogens including SARS-CoV-2, the lights may cause unwanted chemical reactions and should be used with ventilation, researchers say.

Indoor Air Quality Implications of Germicidal 222 nm Light (open access)

Nanoparticles: Everlasting Germ Killer, In Paint, Fabric, Plastic And More

Good news! We presume it is fairly harmless to human health!

Best of all it acts permanently for a long time without refilling etc.

"Nanosono, a startup based in ... Israel, says its doing exactly that. It has developed nanoparticles – less than a millionth of a millimeter – made of zinc oxide and copper oxide. ...

The nanoparticle, known as Quactiv, was originally designed as a powdered additive for fabric and then to paint, to reduce the number of hospital deaths from from infection-related diseases.

“You need one kilogram of Quactiv in two tonnes of paint to get the antimicrobial action,” ... That’s a concentration of just 0.0005 per cent. It’s cost-effective, non-toxic and environmentally friendly ...
Two mechanisms of action work together. One is the electrostatic interaction between the positive charge of the nanoparticles and the negative charge of the microbes. The second is the release of specific free radicals (reactive oxygen molecules) that destroy the functionality of the microbes. ..."

Everlasting Germ Killer, In Paint, Fabric, Plastic And More Germs are everywhere. Think Covid, think superbugs, salmonella, norovirus, and the common cold.

Far-UVC light zaps airborne pathogens in realistic indoor conditions

Good news! If you combine this type of UV light with air filtering, then this should be very effective!

Instead of applying this UV light to the room itself, it should perhaps be applied separately to filtered air external to the room and this air is then piped back into the room.

"Far ultraviolet-C light can reduce the level of airborne microbes in a room by more than 92%, according to a new study by researchers in the UK and the US. ...
A decade ago, researchers at Columbia University in the US discovered that a different wavelength of UVC light, known as far-UVC light, would be just as effective at killing germs, but without the safety concerns. This is because, at 222 nm, its wavelength is too short to penetrate human skin or eye cells. "

From the abstract:

"Many infectious diseases, including COVID-19, are transmitted by airborne pathogens. ... One potential solution is Krypton Chloride (KrCl) excimer lamps (often referred to as Far-UVC), which can efficiently inactivate pathogens, such as coronaviruses and influenza, in air. ... While there is laboratory evidence for Far-UVC efficacy, there is limited evidence in full-sized rooms. For the first time, we show that Far-UVC deployed in a room-sized chamber effectively inactivates aerosolised Staphylococcus aureus. ..."

Far-UVC light zaps airborne pathogens in realistic conditions – Physics World

Far-UVC (222 nm) efficiently inactivates an airborne pathogen in a room-sized chamber (open access)