It's easier - and less expensive - to prevent moisture damage in or resulting from your heating, ventilating and air conditioning system that to repair it. Here's what to keep an eye on.

What to Look for in the Heating System

• Filters are virtual incubators for possible mold growth and should be changed every month.
• If you have a gas heating system it probably generates water as a side effect of combustion. Be sure any moisture has a proper place to drain.
• If you have a boiler system, first be sure there is free air flow to the exterior. Look for any signs of rust. Also, be certain there are no loose fittings.
• If your furnace has wall penetration for fuel or electrical, check the wall seals for any signs of moisture.
• Ductwork is another breeding ground for mold. Be sure to have your ductwork professionally cleaned every five years. If you have pets or smokers in the family, do it every three years. Vacuum the air supply registers regularly.

What to Look for in the Cooling System

• Since heating and cooling systems frequently use the same ducts, everything you should do to prevent moisture damage in a heating system duct applies to the cooling system.
• Look behind the filter when you replace it to see if the heat exchanger coils need cleaning. If so, use the soft brush of the vacuum.
• Clean the drain pans regularly and, when the seasons change, pour a few tablespoons of bleach mixed in hot water down the drain to clan and disinfect it.
• If your air conditioner coils "ice up" it's not a good sign. Call a professional.