Cats don't belong in the ceiling

My cats have shared a room with my stash since we first got them about 6 months ago. I minimized havoc by keeping the stash in dressers and the closet but they still caused some mess. Every now and then they would get into the hutch on my desk and pull out a skein. They only once caused any real damage to the stash and that was because Oni was sick. Unfortunately though kitty litter and carpet are not a good combination. So the cats got moved downstairs.

They adapted very well to the change. This change includes allowing them into the previously off limits laundry room, since that is where the litter box is. It was off limits since they were young and the room is unfinished with exposed pipes and wiring. They are old enough now and have never shown an interest in chewing on wires. What I did not forsee is that they would find a way to get into the ceiling of the rest of the basemet. They had a lot of fun and came out absolutely filthy. I had a lot of thoughts of all the things that could happen (cat stuck in ceiling, cat pee in ceiling, dead cat in ceiling, and where else can thy get to from in there?).

Do you know what it takes to seal off the joist openings in a laundry room? I do. 1 trip to Lowes, 1 staple gun, 35' of plastic mesh, a LOT of staples, some Duct tape, 8 hours, a very sore neck and arms, and 2 allegra for the allergies.