Have you noticed your house getting dusty more quickly than usual lately? Are your utility bills slowly creeping up each month? Dirty ductwork and HVAC system components may be to blame. If your home is older or has experienced significant water damage, consider hiring a reputable, professional duct cleaning company to clean your home’s ductwork.

How is air duct cleaning done? The correct method uses negative pressure technology. Negative pressure air duct cleaning is a methodical, straightforward process that delivers clear results, but less-than-reputable, fly-by-night companies have given the industry a bad rap in recent years. 

If you’ve had your ducts cleaned by a company that was in and out in an hour and seemed to leave more dust and dirt than they actually removed, you were probably left wondering exactly what, if anything, was done.

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To combat these negative experiences, legitimate duct cleaning contractors are eager to educate homeowners about the National Air Duct Cleaning Association’s (NADCA) standardized methods for cleaning services. 

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.

How Duct Cleaning Works

close-up image of dirty air vent

Step 1: 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 that you can take yourself 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, a professional duct cleaning is an opportunity for the technician to check the ductwork for leaks or, in the case of flexible ducts, kinks. Many duct cleaning contractors can also make repairs and replace damaged ductwork.

Step 2: Create negative pressure

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.)

  • Next, the technician should seal each register with an adhesive cover. This is an important step because even an extremely powerful vacuum collection device will be ineffective if the registers in each room of the house are uncovered.
  • Once the technician finished these preparatory steps, he or she will turn on the vacuum unit. This step creates negative pressure, and particles inside the ductwork will be sucked into the collection device as they’re brushed or blown loose.

Step 3: 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 4: 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.

The Bottom Line

uncovered ductwork

Does negative pressure air duct cleaning work? Yes! But it must be done correctly and by qualified professionals.

NADCA states that a thorough cleaning should take three to five hours. While this 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. Hire a Best Pick duct cleaning contractor to ensure that you receive service that meets the industry standard for quality.