[coconut_crab]

My N95 mask smells like burnt plastic after 7 minutes under UVC (254 nm), I wonder if that means the mask is damaged.

[remote_phone]

Depending on the intensity of light you have and the wattage is the bulb, 7 mins is way too long. If your bulb is very close to the mask 10 seconds is more than enough.

[koolba]

Can I disinfect other things like mail or a cardboard box with a UV light?

Alternatively, would leaving things under the sun have a similar effect and, if so, how long would it take?

[throwaway2048]

UV-C is basically entirely blocked by the ozone layer and doesn't reach the surface of the earth.

Its extremely dangerous, and can cause eye and skin damage with under 60 seconds of exposure, it is absolutely something you do not want to be anywhere around when active.

[nfpfish]

UVC is safest actually. Short wavelength is absorbed by dead skin cells. Never gets to live.

[dheera]

Is there a good reference on how to calculate the time based on the wattage W and distance of the bulb D?

[K-V]

Just want to not 254nm does not kill the virus, it requires 222nm UV-C. Only one manufacturer exists in the US for the bulbs AFAIK.