How to clean your air ducts

How do I know if my air ducts need to be cleaned?

Look for the following signs and symptoms of dirty air ducts:

Dust around vents

“Is there a layer of dust built up on the slats of your vent covers? If so, there’s a good chance your ducts have a layer of dust too,” said Walenty Bednarski, an indoor air quality specialist. “Another telltale sign is a puff of dust from the vents when the furnace kicks on.”

Visible mold growth

Mold and mildew can’t grow in clean air ducts. Remove a few of your vents and shine a flashlight inside. If you see anything growing either inside or around the vent covers, it’s definitely time for a duct cleaning.

Unpleasant odors

“Notice a bad smell in your home, but can’t pinpoint the source? It could be dirt and debris in your ducts,” said Bednarski. “Go around smelling them carefully if you suspect this, or call in a professional to get to the bottom of things.”

Allergy or respiratory issues

I once entered the home of a friend and immediately started sneezing uncontrollably. Turns out his air ducts were full of mold and rodent nests. “If your breathing is being noticeably affected when you enter your home, chances are fairly good that dirty ducts are why,” Bednarski advised.

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How to clean your air ducts

Cleaning your air ducts requires multiple tools. You may have some of them already, but others may require a trip to the hardware store. Things you'll need include:

• Shop vac with long hose attachment
• Powerful electric leaf blower
• Flexible extending duct cleaning brush
• Drill
• Screwdriver
• Cardboard
• Concrobium mold control spray
• Wide masking tape
• Wool insulation
• Respirator

Directions for cleaning your air ducts

To safely clean your air ducts, follow these steps.

Be sure to wear a respirator as you work so you don’t breathe in any dust and debris.

1. Switch off your furnace or any other appliances designed to move air through your ductwork.
2. Remove all heating vent covers and cold air return covers in your home, and then use your shop vac to vacuum away any dust and debris you find inside each vent as far in as your vacuum hose can reach.
3. Cut one piece of cardboard for every heating and cold air return vent in your home, making the pieces slightly larger than the vent opening. Fasten each piece of cardboard down firmly over its opening with masking tape, except for the heating vent furthest from your furnace.
4. Locate the access ports for cleaning in the bottom of your heating and cold air return ductwork. Remove the cover plate on the heating duct access port.
5. Insert the end of your shop vac hose into the access port, then stuff wool insulation into the duct behind the hose to prevent dust and debris from moving past the vacuum and into your furnace.
6. Go down to your basement and switch on the shop vac. Keep it running as you return to the furthest heat vent from the furnace.
7. Slide your vent cleaning brush into the vent, then attach the non-bristle end to a drill. Run the drill at low speed to rotate the brush inside the duct as you extend it further. When you run out of brush length, detach the drill and thread on another length of brush handle. Reattach the drill and repeat the process until you’ve gone as far as the brush will allow. Remove the brush, detaching each segment as you do.
8. Stick your leaf blower inside the furthest heat vent from your furnace, then seal the vent around the leaf blower using wool insulation. Switch on the leaf blower and run it for a couple minutes, giving it time to blow all the freshly loosened dust down the duct and into the running shop vac.
9. Repeat the process for the rest of the heating vents in your home, making sure every vent not being cleaned is sealed with cardboard.
10. Transfer your shop vac to the main cold air return duct, close the main heat duct, and then repeat all the same cleaning steps for each cold air return vent and duct in your home.
11. Spray and wipe down any vent covers and ductwork that have mold or mildew with mold control spray.

How much does it cost to clean your air ducts?

If you hire a professional duct cleaning company, expect to pay anywhere from $450 to $1,000, depending on the size of your home. This cost range is a good ballpark but is subject to change depending on the accessibility and layout of your HVAC system and furnace. Exceptionally dirty, moldy or vermin-infested ducts will likely cost more than normal to clean, particularly if extra workers are needed.

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Some home warranty plans cover the cost of cleaning your air ducts. Read your contract carefully or ask a company representative what's covered under your plan.

Cleaning your own air ducts will almost certainly be cheaper, provided you already have the required tools. If you own a good shop vac and leaf blower, the only cost besides your time and effort will be for some wool insulation, tape, an extending duct cleaning brush (about $40) and cardboard. You may even have these items lying around, in which case your only cost will be time, the brush and elbow grease.

Tips for maintaining clean air ducts

Once you’ve put in the time and effort to clean your air ducts or hired someone to do it, it’s only reasonable to want them to stay clean as long as possible. Here are some simple things you can do to keep dust at bay.

• Clean your air ducts every three to five years. Massive buildups of dust and debris are harder to clean, so cleaning a bit more often makes sense.
• Change your air filters regularly. All modern furnaces and heat pump systems come with replaceable air filters to prevent dust from getting into your ductwork in the first place. Swap out both filters every three months to ensure they’re doing their job.
• Keep your house clean, vacuuming often enough to keep dust off your floors and walls.

Bottom line

Keeping your air ducts clean is one of the best ways to make the air in your home healthier. Everyone living in a home with ductwork can and should take this simple step to prevent respiratory illness. Don’t let saving yourself work or a few hundred dollars cost you the freedom to breathe freely.

You can tackle air duct cleaning yourself, but even though I’m an avid do-it-yourselfer, I personally prefer to hire a professional. Their equipment is better, and the job they do will almost certainly be more thorough.

That said, DIYing this job can still improve your home’s air quality — especially if you do it often enough to prevent much dust from accumulating. Besides keeping your ducts clean, be sure to swap out your system’s air filters regularly, and break out the vacuum often enough to prevent visible dust. Your lungs will thank you for it.