How to Clean Furnace and Air Conditioning Ducts at Home

While doing a deep dive, move every piece of furniture that isn’t nailed down Spring Cleaning I noticed several of the heating and central air conditioning ducts had a black soot like dirt or dust collecting around the register grill on the wall and ceiling.   I vacuumed them with the brush and hose on my vacuum sweeper and made a mental note that I need to add this task to my deep cleaning  checklist.

A few days later it was back.

So. Gross.

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Why do I have Black Stuff Around my HVAC Registers?

It didn’t take much in the way of investigating to find out why almost all of the HVAC registers in the house were unusually dirty including the  air purifier filter in our bedroom:

• While I change the HVAC air filter on the first of each month (so I remember to do it) I apparently I didn’t slide the furnace filter all the way into place several months in a row. The furnace filter wasn’t able to do its job correctly, if at all. Dust had been blowing around unfiltered in a closed up for winter house.

• My husband and I never had the furnace duct and air vents cleaned when we moved into our condo after it was built. We figured the ductwork would be clean since it was new with the house. We found out how wrong we were based on some of the things we found when we had to clean the ducts ourselves. So. Much. Sawdust.

Under normal circumstances, I’d call a heating and cooling company to come out and  thoroughly  clean our ducts. Unfortunately we are under lock down. My dust allergies are in overdrive and with pollen season just around the corner, we did a quarantine DIY duct and air vent cleaning. Cleaning the air vents ourselves got the majority of the dust and dirt build up from our duct work, kept the registers from spewing dirt, and made me breathe a bit easier during allergy season.  Once the world recovers from the current apocalypse, we will schedule a cleaning appointment with a pro because there are some areas of our home’s ductworks that can’t been cleaned well without the high powered equipment of a professional HVAC cleaning company.

Do you want to give cleaning your houses furnace and air conditioning ducts a try in the meantime? Here’s how!

DIY Air Vent and Duct Cleaning Tutorial

If you find mold or mildew at any step of the duct cleaning process stop what you are doing and call a pro immediately.

You will need the following tools:

Safety glasses like these – unless you like dust, dirt, and crud blowing into your eyes and especially from ceiling ducts and registers – yuck (Disclosure: I am including affiliate links in this post for your convenience.)

Dust mask or bandanna – You really should wear a face mask because dust, dirt, and crud will be blowing into your face and lungs as you clean the air vents. Under normal circumstances, I would recommend the N95 dust mask  I use them in my woodshop when sanding but our front line medical heroes need N95 filter masks more which is why I am not linking to them at this time.  I didn’t have any  N95s in my shop for this project. I punted and sewed a cloth face mask from a YouTube video. 

My husband calls this my Mad Scientist look. He isn’t wrong.

Wet Dry Shop Vacuum – You will need to use something that is more powerful than a regular home vacuum cleaner. While many of my male friends swear by bigger is always better when it comes to a shop vac (because boys. Am I right?)  I prefer and recommend this exact Craftsman wall mounted 5 horsepower shop vacuum because it has the same horse power as the giant size wet dry vacs but isn’t too big to carry up a flight of stairs or empty without help when it is full.

Dryer vent brush like this kind


Step by Step How to Do It Tutorial


1. Turn OFF the heater/furnace/Air Conditioning. Do not skip this step, especially if you have a gas powered furnace – the dust and debris could catch fire. Yikes!

2. Close or cover the return registers/air vents  in every room of your house. How do you know which vents are the return air registers? The return vents are the vents that have a damper that closes with a little wheel, lever, or manually by removing the register from the floor and closing the flaps with your hand.

An example of a closed return air register vent. We'll clean it and wipe it down in Step 9.

3. Locate and leave the heating and air grills open/unblocked. How to do you which vents are the heating and air grills? The heating and air grills are the vents that do not close. They generally located on the wall (although they are sometimes in the ceiling or floor of your house) and you generally only have one per floor (as always your architecture may vary.) The air vent pulls air into your HVAC system to heat or cool it. The furnace/central air conditioning  sends the heated/cold air throughout the house trough the return vents to heat/cool your house.

4. Set the central air conditioning/furnace to FAN ONLY and let it run for a bit. This will allow some of the yuck in your ducts to blow free and concentrate where you can clean it with the dryer vent bush in Step 6.

5. Remove the return vent from one room in your house and screw several of the dryer vent brush sections together as needed. I went to town and used all of the sections that came with my vent brush kit.

6. Feed the dryer brush through the open return vent  rotate the brush to catch the dirt and debris on the sides of the duct and remove the brush. Repeat as needed.

7. Remove any dirt and debris you knocked loose from the sides of the return duct by feeding the shop vacuum hose into the return duct and turn it on. Repeat as needed. Don’t skip Step 6 for Step 7 and vice versa. In some rooms the brush cleaned more dust and dirt from the vent (for example the brush pulled up dog air dust bunnies in the master bedroom vent) and in others like our guest bathroom the opposite was true (for example wood chips and cigarette butts clogged the shop vac hose several times in the guest bathroom. Odd. Neither my husband or I smoke and the wood didn’t come from my recent remodel.) I have to admit I wasn't happy the builders used the guest bathroom floor vent as a trash can. That has to be some sort of fire hazard, doesn't it?

8. When you feel that the return register and duct is clean, turn off the shop vacuum and remove the hose from the vent.

9. Clean any dust or dirt from the vent cover and replace the closed return vent cover over the register.

10. Repeat Steps 5 through 9 for every return air register in your home.

 
11. Repeat Steps 5 though 9 to clean the supply register (s) in your house. This is another vent that was not only horribly dirty from not sliding the furnace filter all the way into place (Oops! My bad.) but also had a surprising amount of construction debris left inside the vent.

This is what we found inside  the supply register.

This explains my hacking, coughing, and stuffy nose every time I sat in the chair next to the air supply vent.

12. Remove the current and most likely now very, very dirty furnace/air conditioning filter and replace it with a new clean filter.

Looking for more DIY vent and duct cleaning tools? Check out the following options and ideas – and more! – below!


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