Cause

• Depending on what sort of climate you live in, any room in the house can acquire a musty odor. A basement can be especially troublesome. With a concrete floor and walls, and little to no ventilation, it's no wonder they develop mildew and musty smells. Though the exact source of the musty smell may differ, the ultimate reason is water--too much of it. Too much water lets mold grow and therein lies the problem. To get rid of the smell you're going to have to reduce the humidity of the air in the room so the mold will no longer grow there.
  
  

Methods

• The most obvious fix is the easiest. If the outside air is dry, simply open the windows or vents and locate a few strategically placed fans inside the room to funnel the moist air out. For mild musty smells, this might do the trick. If not, it's time to bring in a dehumidifier to remove the excess moisture in the air. A good starting point for the dehumidifier control is to set it about halfway, or below 50%. Keep the room temperature at 60 degrees or higher and let the unit go about its business. As the room dries out, the mold should stop growing. To kill any lingerers, use a bleach solution to wash down the walls and any other areas you suspect harbor mold. Inspect items stored in the room, especially if you have stuff near concrete walls. Mold can grow on just about anything and you might have to empty the room in order to clean your storage containers.
  
  

Dehumidifiers

• Traditional dehumidifiers require that you frequently empty the reservoir containing water collected from the air. Fancier models have a tube you can run to the outside or into a drain. Also look for a two-stage filter process. The first screens out the large particles and the second catches smaller bits all the way down to 2 microns in size. Make sure the model you're interested in has filters that can easily be removed and cleaned.