As I said, Far-UVC from 200-220nm is supposed to be safe to humans because of our layer of dead skin. This is kind of the whole point of the post and is in the references.
254nm has less energy per photon but it penetrates further through skin, meaning that 254nm is definitely dangerous.
I was curious about how much we could rely on that safety, and it turns out there are threshold limit values (see the sixth slide) for UV-C. Between 200 and 220 nm the TLVs are .02 to .08 J/cm^2 (200 to 800 J/m^2), according to the American Conference of Governmental Industrial Hygienists. At 5W/m^2 (your suggested irradiation) that gives you 40 to 160 seconds of reasonably safe human exposure.
As I said, Far-UVC from 200-220nm is supposed to be safe to humans because of our layer of dead skin. This is kind of the whole point of the post and is in the references.
254nm has less energy per photon but it penetrates further through skin, meaning that 254nm is definitely dangerous.
I was curious about how much we could rely on that safety, and it turns out there are threshold limit values (see the sixth slide) for UV-C. Between 200 and 220 nm the TLVs are .02 to .08 J/cm^2 (200 to 800 J/m^2), according to the American Conference of Governmental Industrial Hygienists. At 5W/m^2 (your suggested irradiation) that gives you 40 to 160 seconds of reasonably safe human exposure.
Apparently those slides contradict the studies cited in my article.
I don’t know which to believe. The rational action is to urgently run more experiments to assess the risk from 200nm-220nm band.
It would be really great if those slides had a references section.