I'm absolutely shocked that this is news to people still. Cutting and welding is dangerous and you really need to know what you are doing. It also never fails to surprise me when we get a new welder at work and they are amazed that they aren't allowed to use their own welding mask. They have to wear ours that have respirators built in. Just about all the metals we work with have toxicity issues; cobalt, thorium, copper, zinc, cadmium, lead, tin, etc.
There's also the sentiment out there that welding is easy and fun and anyone can do it, just pick up a consumer grade MIG and you're rolling!
This could also be an issue just using a handheld torch to heat up a frozen fastener, so it could happen under a number of circumstances, not just welding.
Vapors may decompose to harmful or fatal corrosive gasses such as hydrogen chloride and possibly phosgene.
The warning label kind of understates things a bit unless you know how dangerous phosgene is. Seems like everything says it may be harmful or fatal if something goes awry, but phosgene is a real killer even in very small amounts... I don't think that's common knowledge to your average garage guy.
I can't recall now but was it the reaction with argon that causes it decompose to phosgene? Anyway, some sort of statement that phosgene gas is
extremely toxic and will do
permanent, irreversible damage to your health if inhaled even in the smallest amounts might start to get people's attention.
For me, general warnings don't get my attention, there are just too many out there these days. But if it's specific and detailed, then I pay attention. That's why this is such a valuable post, it has a lot of details about what went wrong and the aftermath so it makes for a powerful lesson. Thanks again for sharing!