There you are, seated in your den and watching your favorite television show, when annoying bits of dust start falling from the register above and landing on your nose.

To clean or not to clean?

The EPA says you should consider having the air ducts in your home cleaned if:

There is visible mold growth inside hard surface (e.g., sheet metal) ducts or on other components of your heating and cooling system. Remember that many sections of your system may not be accessible for a visible inspection, so ask the service provider to show you any mold they say exists. A positive determination of whether a substance is mold can be made only by an expert and may require laboratory analysis. For about $50, a microbiology lab can tell you if a sample sent to them on a clear strip of sticky household tape is mold.

Ducts are infested with vermin, such as rodents or insects.

Ducts are clogged with excessive amounts of dust and debris and/or particles that are released into the home from your supply registers.

Wet and moldy ducts:

If you have insulated air ducts with insulation that has gotten wet or moldy, it should be removed and replaced.

If the conditions causing mold growth are not corrected, mold growth will recur.

Information at can help a consumer determine whether to have their ductwork cleaned.

The following is a duct cleaning scheme on “Dateline NBC”:

You wonder if those particles are a signal of something a bit disconcerting, like a heating and cooling unit with dirty duct-work.

Dust. Skin cells. Hair strands. Animal dander. They all can become airborne and get sucked into the ducts, making up most of the dirt found stuck in them, says Pressley Baker, HVAC coordinator at Trident Technical College.

That dirt does not necessarily become loose and re-enter the air space and compromise the quality of the indoor air, says the Environmental Protection Agency.

If a unit was installed properly, is serviced regularly and filters are changed as needed, the ductwork should never need to be cleaned, Baker says.

Many homeowners are concerned about mold, but Baker says that’s not usually a problem when the ductwork is in the attic because the environment is hot, dry and inhibits mold growth. Those with ductwork under the house that might be lying on the ground in a cool, moist environment that encourages growth might have a problem, especially if it’s flexible ductwork that has degraded.

“Within the last 10 or 12 years, companies specializing in cleaning ductwork have been formed,” says Baker, who says their are no classes for that at Trident Tech. “My personal opinion is that if it’s dirty enough to need cleaning, it needs to be replaced. But it does extend the life of the unit.”

The Environmental Protection Agency also says that ductwork cleaning is in its infancy, but adds it can make no blanket recommendation as to whether they need to be cleaned. It does, however, offer some guidance for the homeowner.

If no one in the house has allergies or unexplained illnesses, and a visual inspection of the inside of the ducts shows no large deposits of dust or mold (no musty odor or visible mold growth), cleaning probably is unnecessary.

“It is normal for the return registers to get dusty as dust-laden air is pulled through the grate,” says the EPA, which recommends vacuuming the registers and removing and washing them.

“Duct cleaning has never been shown to actually prevent health problems,” the EPA says.

Neither do studies conclusively demonstrate that dust levels in homes increase because of dirty air ducts or go down after cleaning.

“While the debate about the value of periodic duct cleaning continues, no evidence suggests that such cleaning would be detrimental, provided that it is done properly,” the agency says

When ducts are cleaned, the job should include both supply and return air ducts and registers, grilles and diffusers; heat exchangers; heating and cooling coils; drip pans; the fan motor and fan housing; and the air handling unit housing, EPA says.

The job should be done by a qualified technician, and it is suggested that the consumer contact the National Air Duct Cleaners Association, a nonprofit trade group, which has a certification program for HVAC technicians, to find a qualified technician.

Most of those companies with personnel who are certified are listed on its website: NADCA advises calling on those who claim to be certified but will not be listed until its next site update.

Local cleaners

“Generally, I recommend cleaning every five years,” says Mario Colangelo, owner of AdvantaClean of the Lowcountry, one of about five firms with certified technicians in the Charleston area.

“When homeowners don’t change their filters when needed, they could need ductwork cleaned more often. When filters are dirty, air can go around the filter, into the system and be spread throughout the house,” Colangelo says. “First thing, we will inspect and make sure you actually have dirty ducts.” That would be done by looking inside the ducts with the aid of a camera that has a light on the end.

But there is no set amount of debris that indicates a cleaning is needed, Colangelo says. He considers whether the ductwork has ever been cleaned, how long since a cleaning and whether the customer is having problems with the indoor air.

“A lot of it is subjective,” says Colangelo, who adds that when a customer insists he needs his air ducts cleaned, the company complies. The technician should show the customer the debris collected if the customer asks to see it.

Homeowners needing to clean their filters more than once a month probably have dirty ductwork, says Bill Longman of Longman’s Duct Cleaning Service, another company that uses certified personnel. Those who swipe the inside of their returns with white terry cloth and find it’s very dirty also should consider cleaning their ductwork.

Clean ductwork might not prevent someone from having asthma or respiratory problems, but it can be a tool in improving air quality and helping them to get some relief, Longman says.

Estimates provided by the two companies indicate that servicing ductwork takes from four to eight hours, depending on the size of the house. Homeowners usually will pay from $400 to $800 in houses with one system.

Reach Wevonneda Minis at 937-5705.