One of the demo experts started to tear out the hallway ceiling and came running out with a terrified cry of “HORNETS”! The guy was very allergic and would have had to take lots of Benedryl or get to a hospital had he been stung. Luckily he was not and I was able to buy some foaming hornet spray to take down this nest. (At dusk with the tear out completed in the morning.)
Another reason to be sure the building is sealed both outside and inside.