Ed Currie says he gets x generations a year but have never read how he manages that. Am willing to bet it is with a lot of light and CO2 in a tent or some other way to seal them up. Makes for growing out cross breeds much faster. So there is certainly cause for tents / sealed areas. I am just not that rich.
What you said about fire. Yep, I forget my blessing. I live in a house that used to have a cistern. Former owner drained it, cut a doorway into the basement wall, and installed a thick steel door. Strangest thing, he also ran electric into the place and the door is in a closet. I have to vent the hell out of it or it gets too humid, but I think I could have a bonfire in there and not worry about the house.