I’ve appreciated your content on far-UVC, and I made this account just to ask this question, because I’ve been looking all over the internet and haven’t found any answers: apart from ozone, how much data is there on photodecomposition? I’m particularly concerned about whether there’s the potential for phosgene to be produced if chlorinated solvents are exposed to the lamps.
Here is a setup for producing phosgene at room temperature by exposing oxygen and chloroform to UV light at 184.9 nm and 253.7 nm. I don’t know enough about this sort of chemistry to determine whether the absorption bands are sharp enough that 222 nm light would produce substantially less phosgene, or whether the light from the germicidal lamp just isn’t intense enough to produce dangerous amounts of phosgene even if someone sprays chlorinated degreaser everywhere.
It may be that someone with a lot more knowledge has already dismissed this as obviously not a problem, and that’s why there’s no mention of it. However, since I cannot tell the difference between that and a potentially fatal (if unlikely) hazard being overlooked, I thought it best to ask.
Thanks for asking about this! I just did a little research, and while it looks like the frequency range at 222nm would likely be sufficient for this reaction, there are three reasons why it’s not a concern in practice:
The UV light is not very strong: levels that would produce appreciable toxic gas would already be unsafe for human eyes and skin
Cleaning products almost always contain stabilizers to absorb free radicals
Human spaces have some ventilation (or we’d get too much CO2!) so any tiny amounts that were produced wouldn’t build up
I’ve appreciated your content on far-UVC, and I made this account just to ask this question, because I’ve been looking all over the internet and haven’t found any answers: apart from ozone, how much data is there on photodecomposition? I’m particularly concerned about whether there’s the potential for phosgene to be produced if chlorinated solvents are exposed to the lamps.
Here is a setup for producing phosgene at room temperature by exposing oxygen and chloroform to UV light at 184.9 nm and 253.7 nm. I don’t know enough about this sort of chemistry to determine whether the absorption bands are sharp enough that 222 nm light would produce substantially less phosgene, or whether the light from the germicidal lamp just isn’t intense enough to produce dangerous amounts of phosgene even if someone sprays chlorinated degreaser everywhere.
It may be that someone with a lot more knowledge has already dismissed this as obviously not a problem, and that’s why there’s no mention of it. However, since I cannot tell the difference between that and a potentially fatal (if unlikely) hazard being overlooked, I thought it best to ask.
Thanks for asking about this! I just did a little research, and while it looks like the frequency range at 222nm would likely be sufficient for this reaction, there are three reasons why it’s not a concern in practice:
The UV light is not very strong: levels that would produce appreciable toxic gas would already be unsafe for human eyes and skin
Cleaning products almost always contain stabilizers to absorb free radicals
Human spaces have some ventilation (or we’d get too much CO2!) so any tiny amounts that were produced wouldn’t build up