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Tell me about it. I worked for 3M owned Saint Gobain running kevlar and fiberglass sheets thru 5-story oven feeds. it was often 105°F on the floor, but if you were unlucky enough to lose your line you'd be hiking up 5 stories of oven stacks where temps would be soaring. Not to mention every Friday PM shift would start with running junk lines super hot to "clean" (burn-off) all the accumulated Teflon in the oven walls and exhausts (which did not work efficiently enough) from the prior week. So, at 3PM you would start your shift already drenched in sweat watching as a Teflon smoke plume formed at the ceiling of the 7-story plant, like a dark storm cloud, and slowly make its way down to the floor. By 10PM we would all be coughing and exhausted, scratchy throats, etc.

A lady on 3rd shift who ran my machine had a near death incident and the company swept that under the rug along with plenty of other seriously concerning practices.

AMA!

2 comments

That job sounds like literal hell on earth.

I don't doubt those temperatures at all. But do you know what the relative humidity was? It's the combo that causes problems fast. 100 F and 60% RH is miserable and dangerous, but that's a wet bulb of about 90 F, so there's some marginal potential for your body to cool itself. 100 F and 95% RH is a WB of 98.6 F. Any heat generated in your body has no where to go.

A funny thing happens to those who live or train in extreme environments, their body adapts over time. You or I might pass out if we were suddenly exposed to that sort of factory environment, but an experienced worker might handle limited exposure just fine. The human body is amazingly adaptable.

Nah, that will literally kill any human in potentially minutes. No one can heat adapt to 100F + 95% relative humidity. It literally will cook you dead.

Not at all. I've spent plenty of time (sessions exceeding an hour) in saunas that were >105F and >95% humidity (literally so much steam that it was continuously raining from the condensation).

Remember that when you get a fever, your internal body temp can jump to 103+ and stay there for days. Even at a wet bulb temperature above 110, it's going to take time for your internal temperature to heat up to that level. There's nothing "potentially in minutes" about it for humans that are used to the heat.

Sure, you do eventually have to get somewhere cooler. But a wet bulb temperature of 105F is not going to be fatal for a well adapted human even after a few hours.

Nah. This doesn't pass the smell test.

Throughout much of the Southeastern United States, we regularly see Summer temps above 100F (37C), and humidity up to 90%.

One of the two Marine Corps training bases is in South Carolina where temps and humidity are often near these values and sometimes crest them.

Most of Florida frequently passes these values every Summer.

While it is not comfortable, I can assure you, most humans are able to exert themselves without being killed in minutes from this kind of exposure.

Those do NOT occur regularly in the US at the same time (because the humidity peaks in the morning, but the temperature in the afternoon). Maybe in a few decades though.

35°C at 100% humidity is about the human survivability limit (at 6h exposure). This makes a lot of sense because humans generate ~100W of heat, but require their core temperature to stay constant-- if the environment is too hot and evaporation ineffective because of humidity, then your thermoregulation just breaks down and you die, just like from high fever.

Nope. A human that is regularly exposed to such environments has probably developed a strong cutaneous vasodilation response and can tolerate limited exposure just fine. Instead of a cold plunge in a frozen pond, they're doing a sauna. Human bodies are amazingly adaptable.

Oh, I didn't mean to imply I experienced any force field effects. I dont recall the humidity, but I do recall looking up OSHA rules regarding heat, and they only offer "guidance", nothing is regulated or enforced solely based on the temperature but they do reference relative humidity.