When rats die under your house, the odour can be unbearable. The smell will last anywhere from 10 days to a month. The best way to handle this is to prevent it if possible. Use traps instead of poison. However, if a rat has already died under your house, there are a few steps you can take to get rid of the offensive smell quickly. In about an hour or so, your house will smell like it used to.
Locate the dead rat and remove the carcase. This is the most important step. You might have to crawl under your house to find the rat, but if it isn't removed, the next steps will not be helpful. Wear gloves when handling the carcase, and put the rat in a zip-close bag. Dispose of rat in an enclosed garbage bin outside.
Set off Big D Odor Control Foggers under your house and in your house. Inside your house, you can set them off in your air conditioning system with the A/C turned off. Place the device behind the filter in your central air conditioning system. Do not turn A/C back on until fogger is empty.
Leave the house for about an hour. When you return, the odour should be gone.
This same method can be used for rats who die inside your walls. Locate the rat, dispose of it, and set off Big D Odor Control Foggers in your house to remove smell. One can of Big D Odor Control Fogger can be used per 6,000 cubic feet for those who don't have air conditioning.
Always be careful when handling dead animals. Wash gloves thoroughly after touching a dead rat.