Out with the bad air

I once scrapped out a mechanics shop, and they had exhaust ductwork built in under the slab. They had metal access plates built into the slab connected to the ductwork, and they had a sliding/rotating door in the plates to plug your exhaust hoses into. It was quite slick and very clever. The plates were strong enough to drive over, but not obtrusive to trip over, and the door was spring loaded so you wouldn't inadvertently step in an open hole.