what is the hottest temperature you can work under?

Answer 1

it all depends on how well you're conditioned, and how well protected from excessive heat you are

in the USAF, I sometimes worked in 128F environments for 15-30 minutes at a time, before rotating to a "cool" (95-100F) environment for 15-30 minutes at a time, then repeating the cycle.

i could almost always have gone 5-10 minutes longer under the heat cycle without suffering a reduction in performance attributable to fatigue or heat stress.

that was while wearing the old-style "green fatigue" uniform, but i've done almost as well using the BDU ("camo") uniform.

if tasks are not complex (IOW, to the extent that tasks rely on "muscle memory" rather than intellect and judgment), human endurance can be extended by several multiples of the aforementioned times.

certain firefighters and rescue personnel work directly in environments in which localized temperatures can be more than 1000F, but their bodies are protected from that heat by their suits.