For health reasons, you need to be alert to whether or not you have mold in the basement. Basements are prone to mold if steps are not taken to prevent it. First you need to ensure that your basement stays dry. Wet basements are the perfect place for mold to grow. There are many causes of moisture in basements; all of them can be successfully addressed. Check the basement systematically. That is, move furniture and boxes or other items so you can see the floor and walls in behind. Do not forget to check the items you are moving. Mold can start on the wooden legs of furniture if they happen to be damp. If you find that you have a wet basement, this must be addressed right away. This is step one in mold mitigation.
Wet basements can be the result of many different situations. If you have an older home, it may be that there was no moisture barrier in stalled at the time of construction. If perimeter drain tile were placed around the basement they possibly have settled collapsed or are plugged with roots from the shrubs. Be aware of the soil make-up around the foundation. If it happens to be clay or other poor drainage soil, you definitely need to ensure there is a storm drain to take water away from the basement. Be sure to note if there are any cracks in the concrete. If cracks are found they should be sealed.
Musty basements are easily identified. You smell the must as you enter the area. What you smell is mildew that is growing somewhere in that area. If you have carpeting in the basement, get it out of there and take the under padding as well. These are great things to grow mold or mildew in. Next you need to wash concrete floors and walls with a bleach and water solution of about 3/4 cup of chlorine bleach to 1 gal. of water. After you let the solution sit on the concrete surfaces for about 5 minutes rinse and dry. Now if you are sure you do not have a wet basement, install flooring that will not hold water. Ensure that there is no mold growing in the walls and take all steps to keep the basement dry.