CDC wrote:

CDC recommends wearing cloth face coverings in public settings where other social distancing measures are difficult to maintain (e.g., grocery stores and pharmacies), especially in areas of significant community-based transmission.

CDC also advises the use of simple cloth face coverings to slow the spread of the virus and help people who may have the virus and do not know it from transmitting it to others. Cloth face coverings fashioned from household items or made at home from common materials at low cost can be used as an additional, voluntary public health measure.

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The rates of all infection outcomes were highest in the cloth mask arm, with the rate of ILI statistically significantly higher in the cloth mask arm (relative risk (RR)=13.00, 95% CI 1.69 to 100.07) compared with the medical mask arm. Cloth masks also had significantly higher rates of ILI compared with the control arm. An analysis by mask use showed ILI (RR=6.64, 95% CI 1.45 to 28.65) and laboratory-confirmed virus (RR=1.72, 95% CI 1.01 to 2.94) were significantly higher in the cloth masks group compared with the medical masks group. Penetration of cloth masks by particles was almost 97% and medical masks 44%.

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"UV lamps should not be used to sterilize hands or other areas of skin as UV radiation can cause skin irritation," WHO says.

"You can catch COVID-19, no matter how sunny or hot the weather is. Countries with hot weather have reported cases of COVID-19," WHO added.

neal10a wrote:

There is nothing new about using UV for killing bacteria and viruses. It has and is being used for treating well water for years. I had a UV water system in a prior home I owned and it did a great job killing harmful bacteria. Sunlight contains UV and is limited or it would kill plants and animals if it had a higher concentration. Even its lower radiation level causes skin cancer for some people. Also it purifies mountain water streams as well, making it safer to drink directly from a high mountain stream. Many pioneers, trappers, Indians, and others new that. It makes it easier to understand that it could purify air handling systems as well.
Here is one vendor: https://www.skillingsandsons.com/blog/the-pros-and-cons-of-using-ultraviolet-rays-for-water-treatment

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We have previously shown that 207-nm ultraviolet (UV) light has similar antimicrobial properties as typical germicidal UV light (254 nm), but without inducing mammalian skin damage. The biophysical rationale is based on the limited penetration distance of 207-nm light in biological samples (e.g. stratum corneum) compared with that of 254-nm light. Here we extended our previous studies to 222-nm light and tested the hypothesis that there exists a narrow wavelength window in the far-UVC region, from around 200–222 nm, which is significantly harmful to bacteria, but without damaging cells in tissues.