Duct cleaning is a methodical, straightforward process that delivers clear results. However, you might not know it from watching cheap, fly-by-night duct cleaning contractors work. 

Their spurious methods often take a fraction of the time as an accredited professional’s, and disappointing results can leave a homeowner wondering exactly what, if anything, was done.

Unlike their industry’s outliers, legitimate duct cleaning contractors are eager to educate homeowners about the National Air Duct Cleaning Association’s (NADCA) standardized methods. 

These procedures establish how to properly clean ducts as well as registers, filters, plenums, evaporator coils, and air handlers—almost every component of a forced-air HVAC system—and the results will be obvious.

The methods used by accredited contractors are called source-removal techniques by NADCA, and they involve cleaning the ducts by hand and with compressed air tools while a vacuum collection device extracts dislodged dust and debris. 

Read on to understand more about the duct cleaning industry’s best practices.

Step One: Inspect the Ducts

A simple visual inspection of the ducts leading to the return and supply registers is important for two reasons. First, it’s a step homeowners can take themselves to assess the level of buildup in the ducts beforehand and confirm the difference after they’ve been cleaned. 

(A duct cleaning contractor will likely have cameras that can probe even farther into the ducts and show the full extent of the buildup prior to cleaning.) 

Second, when a professional performs the inspection, it affords an opportunity for the technician to check the ductwork for leaks or, in the case of flexible ducts, kinks; many duct cleaning contractors are also capable of making repairs and replacing ducts.

Step Two: Create Negative Pressure

Basically, duct cleaning contractors use large, portable or truck-mounted vacuum collection devices to suck dust and debris out of your ductwork. However, before turning on the suction and scrubbing the ducts, the technicians must perform a few preliminary steps. 

First, they must hook the vacuum collection device’s large hose to a duct close to the air handler—the heart of your HVAC system. The technician will simply cut an access hole in the duct, insert the vacuum hose, and seal where they join as tightly as possible. 

(Note that your HVAC system includes a supply side and a return side—ducts that send treated air into the rooms of the house, and ducts that return air to the air handler. The supply side and return side are separate, and the duct cleaning process must be performed on each.)

Even an extremely powerful vacuum collection device will be ineffective if the registers in each room of the house are uncovered, so the technician should seal those with adhesive covers.

Turning on the vacuum will now create negative pressure, and particles inside the ductwork will be sucked into the collection device as they’re brushed or blown loose.

Step Three: Agitate the Dust

Once the system is under negative pressure, the technician will uncover each register and clean the ducts one by one. One thing that distinguishes a NADCA-certified duct cleaning contractor from a fly-by-night is the amount of time each spends per register. 

Improperly trained technicians have been known to move on after a quick burst from an air compressor and a spritz of disinfectant; this technique is largely ineffective and usually results in dust being blown back into the room. 

Legitimate technicians will use rotating brushes, compressed air tools, and simple vacuum cleaners to ensure dust is dislodged and sucked into the vacuum collection device.

Step Four: Clean the Rest of the System

NADCA recommends cleaning the other components of the HVAC system as well, including the air handler’s blower motor, evaporator coil, and drain pan. 

Cleaning these components, along with cleaning or changing the filter, will improve the air quality in your home as well as extend the life and increase the efficiency of your HVAC system. To find out more about these particular tasks, read our maintenance tips for improved HVAC efficiency.

NADCA states that a thorough cleaning should take three to five hours. While the service might cost more than what an uncertified contractor charges for a brisk cleaning, the results of a cleaning performed according to NADCA’s best practices will justify the time and cost. 

A properly trained contractor will perform the job thoroughly and carefully, ensuring that your ductwork winds up clean and undamaged. Use EBSCO Research’s listing of local Best Pick™ duct cleaning contractors to find a company that meets the industry standard for quality service.

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