Cat smell or cat urine smell?
If it is the latter, I have had success with Nature's Miracle. If the smell is just the animal, that will diminsh with time and with changing out blinds, flooring, wall ... read more
Verify that all window and door seals/weatherstriping is in good shape.
Check to be sure doors and windows are caulked properly (no gaps, cracks or missing).
If you have an attic access, treat it like ... read more