Four words. Cat urine and Bleach. It was really bad. The ferals had a party in the bathroom I put them in because of the nasty weather. I cleared them out and had to dump everything out of the cat box but it was soaked all the way to the bottom with urin. I mean soaked. Without thinking about it I tossed a splash of bleach on it. ( I know I KNOW, but I wasn't thinking clearly!) It started to fizz and fumes exploded forth. The instant the bleach hit the urin I threw open the window and fled. I stuffed a blanket under the door and now I'm afraid to return. I'm coughing my head off now and my nose and eyes are burning. Anyone know how long it will clear out? I really really really do not want to breath in mustard gas. I have this thing about wanting to live. Corrected because I can't count.