How to Clean a Furnace (and why it's important)

Two air vents in the sun against an orange wall

We recommend getting your furnace professionally cleaned at least every other year - and, of course, we’d be more than happy to help you do that. But when it comes to your own home maintenance, you can learn how to clean a furnace yourself. You don’t even need any special materials to learn how to clean a furnace - with a little bit of elbow grease and some standard household cleaning tools, you can make sure everything is in its best possible shape.

Why Is It Important to Know How to Clean a Furnace?

Making sure your furnace is in tip-top shape is crucial, especially every year just before winter. No one wants to be grappling with furnace issues in freezing weather! So seize the moment to preempt any problems down the line.

There are a variety of issues that a dirty furnace can cause, and ultimately, if dirt builds up inside your furnace, it will eventually stop turning on. That’s why it’s so important to check it out regularly. Learning how to clean a furnace now can save you time and headaches down the line.

One issue that can crop up and stop your furnace from turning on is a thermocouple malfunction. A thermocouple is a temperature-sensitive electronic device that responds to the heat of the pilot light by keeping the gas on. If it is dirty, it can malfunction and the pilot light will stop turning your main flames on when the furnace turns on, which is why it is so important to learn how to clean your furnace.

Another problem that learning how to clean a furnace will help you to prevent is circulating dirty air. When dirt builds up in the blower assembly, which is the part of the furnace that blows the air through the flames and back out to the house, then all the air passing through the furnace will pick up the dirt and spread it throughout the house. For information on how to clean your air ducts to keep the air circulating around your house as clean as possible, check out our guide here.

So let’s dive in. Here are the steps for how to clean a furnace yourself!

What You Need to Clean Your Furnace

• A vacuum with a pipe hose attachment

• A mild soap 

• Water

• A stiff-bristled brush

• Cleaning cloths

• A drinking straw

• A paper clip or wire brush

• Optional: a toothbrush

How to Clean a Furnace

Turn the Furnace Off and Let it Cool Down

Unplug it if necessary, turn off all the switches and leave it for a half hour to cool down. When it comes to how to clean a furnace, it’s very important that the power and the gas are cut off.

Remove the Combustion Chamber Door and the Burner Cover

Even if your furnace has an access panel, you will probably need to unscrew and remove the whole combustion chamber door to give you the room that you need to work.

Inside, unscrew the burner door to reveal where the flames are fed.

Check the Burner Flames

This is an optional step in how to clean your furnace, but at this point you can turn the furnace back on and carefully observe the flames from a distance. They should be a deep blue. If they’re yellow, that means the burners are dirty. If you choose to check these, make sure to turn the furnace off and unplug it again, and close the gas valves.

Vacuum the Burner Cavity

Once everything has cooled down, clean the burner cavity with the pipe attachment on your vacuum cleaner, sucking up as much dust as you can get.

Clean the Pilot Light

To clean the pilot light, you can use a paper clip or a wire brush to clear out any little visible bits of dirt around the mouth of the pilot light, and then you can use a normal drinking straw to blow the dust off of it.

Remove the Blower Fan and Clean It

This is one of the most substantial parts of the process in how to clean a furnace. You will have to loosen a few screws to free the blower fan from its compartment, as well as detaching a few wires. You may want to use masking tape to mark which wire ends attach to different parts of the fan.

Now, use the vacuum for a first pass at cleaning the blower, then use soap and water with a stiff-bristled brush, and then with a household cleaning cloth to wash the fan and the assembly. You could use a toothbrush to get between the blades and in the ridges of the blower. 

Vacuum the Blower Compartment

While the fan is still removed, use the vacuum to pick up the dust in the blower compartment. If there is still visible dust and dirt, use a damp cloth to get the rest of it.

Reattach the Blower Fan

Put the blower fan back, reattaching the wires and re-screwing it in. 

Brush and Vacuum the Heating Block

Use the stiff-bristled brush to clean any dirt off from the heating block assembly, following up with the vacuum.

Replace the Filter

Replace the filter with a new one. If you’ve changed it recently, still use this as a chance to pull it out and inspect it to make sure it hasn’t gotten too clogged or damaged. Check out our guide on how often to change your air filters.

Replace the Covers and Turn On the Gas

The final step in how to clean a furnace is to screw the covers back on and turn the gas and the power back on.

You’ve Learned How to Clean a Furnace!

There you have it - the steps for how to clean a furnace! As you can see, it isn’t particularly difficult - just a bit time-consuming. The good news is that you don’t have to do it very often - once a year should be enough to make sure everything is working properly.

Ultimately, you can’t reach every part of your furnace or HVAC system without specialist equipment, so if you want peace of mind with knowing that every part of your ventilation system is sparkling, check out our services.