Find the source of the smell
First, you need to find the source of the smell in the basement. You must perform a thorough inspection of the area and check what could be the source of the problem. Generally, a musty smell is caused by humidity in the area, leaking pipes or any cracks in the walls of the basement.
Clean the place nicely
Remove everything from the area and clean the place nicely. You can add a detergent in a bucket and use a mop to clean the floors. This may take some time but getting rid of the dirt is extremely important.
Make repairs if needed
The next thing you need to do is to get all the walls repaired and any leaked pipes fixed. You can clean the place for some time but the smell will remain if the walls and pipes are not fixed.
Find the solution to the problem
After getting all the repairs done, it is important to find a permanent solution to the problem. One of the commonly found problems in basements is moisture. This problem can be fixed by getting proper ventilation in the area. Cross ventilation is crucial to solve the issue and installing an exhaust fan will help your cause.
Freshen up the place
You can use an air freshener in the end to freshen up the atmosphere in the basement. Open the doors of the place to ensure proper ventilation for some time. Do not use too much air freshener as that can be harmful.