I recall the one time having to work on an old, defunct landfill with a respirator and tyvek suit on in the summer on the east coast. HOT!
After I saw some guy walking his dog in the same area as I was working, I would sneak gulps of fresh air and try to wipe off the fog from the face mask. Probably not a huge deal at an old landfill.
A big no-no in an Ebola isolation tent.
These people are trying to perform surgery and all those other medical things under those conditions. Pretty rough.