A dead mouse or rat can produce odor up to two weeks or longer, depending on how big it is. The larger the rodent, the worse the smell is and the longer the smell can linger.
Using rodent bait to kill these pests often results in the rodents dying within the walls of a home. In a wet environment, the mouse takes longer to decompose or dry out, which can cause the smell to last longer. The warmer the environment, the faster the pest will decompose.
Using a charcoal-activated air cleaner helps eliminate the smell. Some air sprays, particularly odor neutralizing sprays, help to get rid of the smell. Regular air fresheners only last a short time and need reapplying often.