...my wife came home from a chemistry demonstration with a cooler full of dry ice: we thought it would be fun to fill the master bathtub with hot water, dump it all in at once, and watch what happened...
...besides the obvious violent commotion, our entire house filled with a waist-high impetrable fog, enough that we panicked and quickly evacuated the cats lest they be overwhelmed by carbon dioxide...
One slab of dry ice is a couple pounds, I could easily see a bathtub full of it being a problem. Also, co2 is heavier than air, cats are smaller than humans, and they live closer to the ground, so I think ...m... made the right call.