Cat urine has a very strong and unpleasant odor that you can easily detect in a house—even when it's coming from the crawlspace. Because cats tend to mark their territory by urinating, almost every pet owner will have to deal with this problem eventually. Some crawlspaces are accessible to street cats and therefore can become their litter boxes long before you detect the smell. Before you seal your crawlspace, which is the best thing you can do to solve this problem, you will have to know how to remove the smell of cat urine from the crawlspace.
Go inside the crawlspace to look for places where cats have urinated. Bring a shovel and plastic bags so you can remove the contaminated soil. Be careful when removing it so you don't accidentally spread it around even more.
Make a homemade cat-odor removal solution. Take a large plastic container or a bucket. Mix ¼ to ½ cup baking soda, 1 qt bottle of 3 percent hydrogen peroxide and ¼ cup liquid dish detergent. Stir the mixture slowly and carefully.
Pour the solution onto the surface of the crawlspace. Target areas that have been contaminated, but do apply the mixture evenly on the whole surface. Using a spray bottle will make it easier to apply the solution.
Put 1/2 cup baking soda in four to six small shallow plastic bowls. Arrange the bowls around the crawlspace, in four corners and in the middle. This will help eliminate lingering cat-urine odors.
Leave the mixture in a spray bottle for later. It can be used only if it is not stored in an open container.
Seal your crawlspace. Close all openings no matter how small. When it comes to cat-urine smell, prevention is the best solution.