The odour of a dead rodent in your house may be worse than having a live rodent there. You must get rid of the dead rodent in order to get rid of the smell. As long as the mouse or rat is rotting in your house you are going to smell it. But even after the animal is removed, the musty odour may linger for a while.
Locate the dead rodent and dispose of it carefully, wearing gloves and a mask. Dispose of any clothing that comes in contact with the rodent. Scrub all surfaces where the rodent was found with disinfectant. Fill in any holes where the rodent may have entered the room.
Air out the room. Open the windows for a cross-current breeze and bring in an electric fan to get the air moving.
Absorb lingering odours by placing open jars or bowls of vinegar in the room. Alternatively, use an electric air cleaner with an absorbent filter. The filters are made with silica gel or activated charcoal, both of which absorb scent. Other alternatives include odour-remover bags. These mesh bags, designed to be hung in a room, contain volcanic granules that have a natural ionic charge and eliminate smells.
Spray the room with an air freshener or use an odour neutraliser that destroys the microorganisms causing the odour. Odour neutralisers are available in spray and plug-in forms.
If a rodent dies in a wall or under the floorboards, you made need to open a hole in the wall or floor to get rid of the animal and the smell.
Never touch a dead rodent. Make sure your pets do not have contact with the animal.