How important is air-duct cleaning? How often should it be done? Is it worth it to pay the extra money to ensure there is no mold in the air ducts? —Angie's List member Glenn G. Millar

Air-duct cleaning is very important, says Michael Horstman, owner of highly rated Apex Duct and Chimney Cleaning in San Marcos, Calif. "Whatever is inside of the HVAC system is going to be blown out into the living area," he says. "This can cause respiratory issues over time."

When you get ducts cleaned depends on many different factors, Horstman says, including allergies, pets, the house's age and the type of air filter used. "With no major allergies or pets and a quality filter, the time is usually every five to seven years," he says.

Apex charges $40 per vent and Horstman says the average job takes at least three hours. "If a company offers this service for less than $200, you're probably not getting a complete cleaning," he says. Ken Justo, owner of highly rated ASI Hastings Heating & Air Conditioning Inc. in San Diego, agrees. "For a single system cleaning, reputable companies will charge anywhere from $450 to $525," he says. "Some places advertise a small price, but it's pretty much just a Shop-Vac."

Ducts should be tested for mold and Horstman suggests using an EPA-approved biocide sanitizer to clean it. Horstman advises using pleated HEPA or electrostatic filters. Pleated filters should be replaced every 90 days, and electrostatic filters need to be cleaned every month.

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