Over time, HVAC ducts normally build up dust, pet hair, dirt, and pollen. Sometimes, ducts develop mold or they trap larger items like construction debris, vermin, or insects. DIY duct cleaning lets you clean your house's HVAC supply and return vents for far less cost than professional duct cleaning.
How HVAC Ducts Work
HVAC air ducts operate as a continuous loop. Air from the centrally located AC unit or furnace flows through supply ducts and out into the rooms. This air then returns to the central unit via the return duct.
Supply ducts blow warm air or cold air into the rooms. Supply duct registers should be located in most rooms of the house, though some rooms may not be served.
Supply registers are covered with plastic or metal grilles and are found on the floor, on exterior walls, in the ceiling, or under windows.
Supply ducts tend to be cleaner than the return duct. That's because the air first passes through a filter before it makes its way to the various supply registers throughout the house.
Return Air Duct
A large return air vent removes the air from the rooms and returns it to the AC or furnace system. The return is usually located in the wall, close to floor level.
The return air duct is always dirtier than the supply ducts. That's because dirty, unfiltered air from within the home is being drawn down the return duct on its way back to the HVAC system.
DIY Duct Cleaning vs. Professional Duct Cleaning
Cleans last 10 feet of each duct
Debris sent toward the vents
Not all of attached debris in ducts is dislodged
No cutting into ducts
$50 to $100
Cleans entire ductwork
Debris sent back to the HVAC unit
All attached duct debris is dislodged
Possible cutting into ducts to retrieve debris
$450 to $1,000
DIY duct cleaning differs from professional duct cleaning because the professional machines are unavailable to do-it-yourselfers and are hard to duplicate on a DIY basis. This modified, DIY version of professional duct cleaning clears debris from much of the ductwork but does not address the entire system.
In HVAC ductwork, many of the contaminants are attached to the sides of the ducts or are too heavy to be dislodged by air pressure alone. They need to be physically dislodged.
With professional duct cleaning, contaminants are broken up with brushes or air whips attached to compressed air hoses, by hand-brushing, or by contact vacuuming. Professional negative air machines, too, are so powerful that they can dislodge many of the contaminants.
With DIY duct cleaning, a chimney cleaning head attached to 10 feet of flexible nylon rods is sent through the supply and return ductwork. Rotated by an electric drill, the chimney head cleans much of the ductwork but cannot touch all sides of the duct, nor does it move with as much force as a professional duct cleaning company's compressed air-driven whip cleaner.
With professional duct cleaning, while the contaminants are being mechanically dislodged, negative air pressure is applied to the air ducts. This moves the contaminants backward from the return air or supply vents to the main unit.
Air duct cleaning professionals may have to cut into the sheet metal ductwork near the air handler. This allows access to the collected contaminants. The hole is sealed up after the job is done.
With DIY duct cleaning, the contaminants are pulled forward to the vents, not backward to the furnace or AC.
When to Clean Your Air Ducts
For seasonal HVAC systems that operate only at certain times of the year, clean the air ducts about a month before you plan to reactive the HVAC system.
Otherwise, clean the air ducts on an as-needed basis. If the house smells musty when you turn on the HVAC system or if you smell rodent droppings, clean the air ducts immediately.
DIY clean your air ducts, too, after an unusual event, such as installing a new HVAC system, having major repairs, or a dust-creating house remodeling project. Dust and debris that were not moved previously may be moved by running the blower at higher volumes.
Wear a dust mask when DIY cleaning your ducts.
Equipment / Tools
- Shop vacuum
- Shop vacuum extension hose, 10-foot
- Dryer vent cleaning brush with 10-foot extender
- Nylon bristle brush
- Electric drill, with handle
- Dish detergent
- Duct tape
- Replacement HVAC filter
Turn Off the System
Turn off the HVAC system at the thermostat or by shutting off the circuit breaker.
Remove the Grilles
Remove the supply vent grilles and the return vent grilles. Floor supply registers typically are not attached, so they lift off. For ceiling and wall supply registers, use the drill to turn out the screws holding the grilles in place. Return grilles, too, will be screwed into place.
Clean the Grilles
Clean the supply grilles with warm water, mild detergent, and a soft brush in the kitchen sink. The return vent may be too large to clean in the sink. So, wash off outside with the hose, brush, and detergent. Set all grilles against a wall to air dry.
Prepare the Cleaning Brush
Screw the flexible nylon rods together to form a 10-foot pole. Screw the cleaning head onto the end of the rods.
Examine the Supply Ducts
Begin at any supply duct vent. With a flashlight, look inside to see the duct's configuration. Often, the duct will be straight for a short run, then make a 90-degree turn. Sometimes, the duct will reach a tee and turn in two opposite 90-degree directions.
Dislodge the Contaminants in the Supply Ducts
Force the cleaning head into the duct until about 1-foot is exposed at the top of the vent. Chuck the rod into the drill. Press the trigger of the drill forward (not reverse) to turn the cleaning head. While turning, slowly draw out the cleaning rod. When it reaches the end, stop the drill.
If this is a tee, send the cleaning head down the other side of the tee.
Be careful not to turn the drill in reverse. This will cause the cleaning head or rods to detach from each other, embedding these components in the ductwork.
Clean the End of the Supply Vent
With the shop vacuum, suck up the contaminants that the cleaning head deposited at the end of the supply vent.
Prepare the Vacuum Hose
Add the 10-foot extension hose to the shop vacuum. If using a nozzle at the end, secure it to the hose with duct tape to avoid losing it in the ductwork.
Clean the Supply Duct
Turn on the shop vacuum. Force the hose into the supply duct as far as it will go. Slowly draw back the hose. Jostle the hose up and back to reach as much of the vent as possible.
Dislodge the Contaminants in the Return Duct
Similar to the supply ducts, force the cleaning brush and rods into the return duct. Draw it back slowly while rotating it with the drill.
Clean the Return Duct
As with the supply ducts, push the extended shop vacuum hose into the return duct to vacuum out debris.
Replace the Grilles and Vents
When the washed grilles and vents are dry, replace them on the vents.
Turn the System On
Turn the HVAC system back on. Let it run for about 20 minutes. Shut it off and check the filter. The filter will catch contaminants that you weren't able to remove with the vacuum in the return duct. Likely, you will need to discard this filter and replace it with a fresh one.
When to Call a Professional
Thorough air duct cleaning is best done by professional duct cleaners with truck-mounted or large portable negative-air machines that can create a powerful vacuum throughout the duct system.
Coupled with a duct whip to dislodge debris, duct vacuums can pull out debris in far-ranging areas of the duct system, as well as in hard-to-reach corners and bends. Large items like dead vermin and construction materials that cannot be cleaned by yourself can be removed by a professional.