Can anyone recommend a pet-friendly air freshener/odour neutraliser? Having a litter tray obviously results in smells and sometimes I come home to a real whiffy flat! Apart from opening the windows, is there any way to reduce the poopy smells? They use a covered litter box with a carbon filter, I do a complete litter change daily and remove poops as soon as I find them but my babies are still stinking the place out! I'm conscious of the chemicals contained in normal air fresheners and would prefer not to use those, especially in the cats' room.