Both finished and unfinished basements are prone to developing mold-growth problems. If you do laundry, exercise, watch TV, or play in moldy, below-grade (below ground level) space, you may be inhaling mold spores and other unhealthy substances.There are some steps you can take, however, to keep the air in your basement healthier to breathe.Dehumidify. High humidity is the cause of the majority of basement mold problems that I investigate, because certain kinds of mold can flourish when the relative humidity (RH) is above 80%.Dehumidifying a basement - whether finished or unfinished - is therefore the key to mold control. The RH should be kept at or below 50% in in an unfinished basement in the warmer season - in New England, from April to October. Measure the RH with a hygrometer, available in many building supply and hardware stores. If the RH exceeds 50% in an unfinished basement or 60% in a finished, insulated basement, increase the dehumidification.Use a dehumidifier that has adequate capacity for the space (www.therma-stor.com). Keep basement windows closed when dehumidifying. And no matter what anyone tells you, a basement exhaust-only fan is not a dehumidifier. Heat a finished basement. In finished basements, I often find mold growth on furniture legs and on the wooden undersides of furniture, as well as in carpet dust. When air is cooled, its relative humidity rises. When you use finished-basement rooms, you introduce moisture into the space. If you then turn the heat down, the RH will rise and mold may grow in the dust on surfaces, especially those near the cool floor or foundation walls. In the heating season, therefore, a finished basement must be kept consistently warm - at least 60ºF - whether in use or not. Don’t install carpeting  in a finished basement. Mold will grow in carpet dust if the carpet is placed on a cool concrete slab. Install a vinyl or ceramic tile floor instead. Don’t put a rug down on a concrete floor. Sometimes people have their washer and dryer in an unfinished basement, or dedicate a corner of the space as an exercise or play area. People sometimes put rugs down on the concrete to make such spaces more comfortable. Don’t do this, because mold will grow in the dust captured in the rug fibers.

Store personal goods in the right way. Goods stored in an unfinished basement should be placed on metal or plastic shelves, at least eighteen inches away from the foundation walls and six inches up off the concrete floor. This will minimize the chances of mold growth occurring on surface dust and also protect goods in case water leaks from the exterior during a heavy rain.

Never place cardboard boxes on the concrete or up against the foundation walls, because mold will then grow on the biodegradable cardboard. If you must store boxes in the basement, place a sheet of one-inch, foil-laminated, polyisocyanurate foam insulation on the concrete slab and up against the foundation wall, to create an insulated storage nook. This will insulate your boxes from the cooler temperatures of the floor and walls, as well as keep dampness away from your possessions. If any of your cardboard boxes are already water-stained, blackened by suspected mold growth, or smell musty, get rid of them.