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Dust Is Villain in Home Duct Tales

Cleaning the Tubes That Carry Hot and Cold Air to Rooms Can Keep Allergies and Foul Odors at Bay


Everyone in the house seems to have the sniffles. The tables you just dusted yesterday have another coat of film on them. And whenever you turn on the furnace, the air blowing from the vents smells funny.

Is it time to have your ducts cleaned? Maybe, maybe not.

"Most homeowners don't think much about their air-duct system," said Steve Lovsteen of Oliver Twist Chimney Sweep in Long Beach. "As long as air is flowing out the vents, they're happy, but they could have a problem up there."

Despite the flow of warm air from the furnace, all may not be well in your ducts. The system is basically a series of galvanized metal or aluminum tubes that run through the attic to carry heated or cooled air to each room.

Generally one or two "return" ducts draw air from the house into the furnace or air-conditioner, then the outlet ducts distribute it through the home.

Depending on the amount of dust, dirt and pet fur in your home, this debris can build up on the inside of the ducts and be transported to each room. Dust mites can thrive inside these dark spaces, and, for homes near the ocean, mold and mildew can flourish.

This can be a serious problem if someone is allergic to these substances. If that's the case, most allergists recommend air ducts be cleaned regularly.

"If you have pets and/or some kind of construction that's generated a lot of dust, you may need to have it done yearly or every 18 months," said Bob Martin of Serv-Pro in Huntington Beach. "Otherwise, every three to five years should be fine as long as you're changing the filters regularly."

It's not uncommon for some duct-cleaning salespeople to tell homeowners about unsubstantiated health benefits related to the cleaning of air ducts, including a reduction in the amount of germs in the home and in the number of colds you can catch.

But according to a U.S. Environmental Protection Agency bulletin, no such benefits have ever been proved.

Cleaning the ducts is generally beyond most do-it-yourselfers.

"The blower is removed from the furnace, the registers are removed from the walls and the vents are sealed off, then we hook up a high-powered vacuum to the furnace," said Kathryn Laux, who operates Mighty Ducts with her husband, Andreas, in Huntington Beach.

Each vent in turn is then opened. After this is done, a flexible auger, or rotating brush, is pushed through the vents toward the vacuum to flush out any debris stuck to the inside of the ducts.

"The registers are then given a good cleaning," Lovsteen said. "Then the motor and blower are vacuumed and cleaned out. We also use a disinfectant on the blower, and we'll spray it in each duct and let it circulate within the system."

To keep the ducts as dust-free as possible, the filter should be replaced at least annually. You can also add an electrostatic filter, which uses static electricity to draw dust out of the air that's flowing through the house.

Stores catering to allergy sufferers also have filters that can be attached to the registers at each vent.

Generally, the duct-cleaning process takes two to four hours and prices can vary.

"For a good job, expect to pay around $300 to $400," Lovsteen said. "You'll want to be wary of someone who claims that they'll do the whole house for $69. You get what you pay for."

The rule of thumb is to figure on spending about $25 per register in your house. The average 1,500-square-foot house has about seven registers, or one for every 200 square feet.

Unless they have a contractor's license, duct cleaners aren't allowed to repair the furnace or air-conditioning systems or replace ducts.

"Before starting our work, we'll check the flame on the furnace," Lovsteen said. "You want it to be nice and blue. If it's orange, that can mean there's a lot of dust in the burners. If the flame is yellow, that can be a sign of a cracked heat exchanger, which is dangerous."

Making sure your ducts have been properly cleaned can be a little tricky. How can you tell?

"Look to see that the registers are clean and make sure the technician turns on the air-conditioning and the furnace before they leave to make sure they're working," Lovsteen said.

How does one decide whether to have their ducts cleaned?

It's probably best to first see how much of a problem they're creating. The most common call for duct cleaning comes after someone in the household develops allergies. This can be especially crucial to someone who has recently moved into a new home.

"What if you're allergic to cats, and the person who lived there before had three cats?" Laux said. "You may need to have the ducts cleaned out before you move in."

Major remodeling or construction work can also contaminate the air ducts. On projects where there's going to be a lot of dust generated, good contractors will seal off the registers in the affected rooms so they won't collect dust.

After a large remodeling project, cleaning the ducts may be a good way to finish it up.

Overall, duct cleaning may be more of an option for those with allergy or respiratory problems, or who just like to get the ultimately clean house.

"It's like a refrigerator," Laux said. "How often do most people roll it out to clean underneath it? Most of the time it only gets clean when they have to move the refrigerator. Sometimes, even if you don't see it, you feel better if you know something's clean."

More information on air-duct cleaning:

* The U.S. Environmental Protection Agency Office of Radiation and Indoor Air Indoor Environments Division. 401 M St. S.W., Washington, D.C. 20460. (202) 564-9370

* National Air Duct Cleaners Assn., 1518 K St. N.W., Suite 503, Washington, D.C. 20005. (202) 737-2926

* Mighty Ducts, (714) 848-7879.

* Serv-Pro, (714) 841-1695.

* Oliver Twist Chimney Sweep, (562) 595-5122.

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