Some notes on “far UV-C” light

Can we use a new kind of UV-C light in occupied spaces?

In 1903, Niels Finsen was awarded the Nobel Prize for using UV-C light for disinfection, originally for lupus. Since then, UV-C has been used in tackling Tuberculosis and MRSA in hospitals.

Recent interest in UV-C for COVID-19 has involved disinfecting air (since there is potential for the virus to transmit via aerosols), and also for fast surface disinfection.

Historically, UV-C sources have mainly been 254nm lamps, a wavelength very good at destroying DNA/RNA. However, 254nm is not safe to use where people can see it, because it can hurt your cornea. While this kind of light will not make you blind, it hurts: it is described as a gritty feeling right after, with intense pain after that, until your cornea has a chance to regrow.

“Far” UV-C

Recently, work by David Brenner and colleagues at Columbia has included “far UV-C” light from 207–222nm, with 222nm the most promising.

  • Far UV-C (222nm and below) is different than the 254nm tubes that most people are familiar with, mainly because it has the potential to be used to disinfect surfaces in occupied spaces. 254nm should never be used this way because of corneal damage.

Some additional notes about UV-C

  • Many worry about skin cancer. However, skin cancer is mostly in the UV-B range, and so UV-C products do not pose a known skin cancer risk. The reason for this is that they don’t penetrate the outer “dead layer” of the skin, the epidermis. As wavelengths approach 300nm (e.g., some LEDs), we should worry more about this.

For more information about UV-C disinfection (with actual experts), refer to the IES FAQ here.

co-founder of f.lux, finding the connections between circadian rhythms, sleep, healthy buildings, and light. (Previously made Picasa.)

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