What is a Furnace Burner, and Why You Should Keep Them Clean!

What is a furnace burner

⭐ What are Gas Furnace Burners?

Gas furnace burners are an integral component of your furnace. As the name suggests, the gas burners mix air and fuel (in this case, natural gas) and burn it to create heat.

This heat from the combustion process is moved into the heat exchanger, where air passes over it. The heated air is then distributed via your home’s ventilation system. All furnaces that burn some type of fuel contain furnace burners.

These could be powered by natural gas, propane, or oil. Depending on where you live and how much was spent during installation dictates the type of furnace you have.

furnace operation
Internal view of a Central HVAC system during heating

How a Gas Furnace Burner Works

Your furnace heats your home through the combustion of a fuel-air mixture that’s mixed with the circulating air.

How it works can be broken into the following steps:

  1. When your home’s air temperature drops below the temperature set by your thermostat, the thermostat sends a signal to your furnace to start the heating cycle.
  2. The fuel valve opens, sending gas to your burners. At the same time, the air is mixed with the fuel and is ignited by the pilot light.
  3. The heat from the combustion chamber is forced into the heat exchanger.
  4. Circulating fresh air is passed over the heat exchanger within the indoor air handler and out into the rest of the home.
  5. You and your family are now nice and cozy.

Types of Furnace Burners

Depending on your type of furnace, there are a few different styles of furnace burners.

Some, of course, are more popular than others.

The top 3 variants are:

🔥 Inshot Burner:

Inshot burners are used within induced draft furnaces and can be found in all new high-efficiency furnaces.

🔥 Upshot Burner:

Upshot burners are typically used in natural draft furnaces. Natural draft furnaces are common in older furnaces and are slowly being replaced with high-efficiency gas furnaces.

🔥 Conversion Burner:

As the name dictates, conversion burners are used when fuel is required to be converted from one type to another. These are typically fitted during an oil-to-gas conversion.

⭐ Furnace Burner Issues

Gas furnace burners

Furnace burners are an essential part of your home’s heating system. Without it, you would never be able to warm your home.

Maintaining energy-efficient heating systems requires properly functioning furnace burners. Like every system, things can go wrong over time.

Typical problems that can occur include:

🔥 Cracks:

Furnace burners, just like the heat exchanger, are subject to constant heating and cooling.

This constant expansion and contraction can result in cracks.

🔥 Corrosion

A lack of furnace maintenance, moisture buildup, and poor air circulation can cause corrosion. Rust can build up and cause metal to flake off and block the burners.

🔥 Blockages

Again a lack of furnace maintenance can cause your furnace to collect dust and debris, including that from corrosion and reduce the effectiveness of your furnace burners.

A dirty air filter can reduce adequate airflow and possibly introduce other debris into the combustion chamber.

🔥 Insufficient Heat:

The furnace burners could be at fault if your furnace is not heating your home properly.

If you’re not a confident DIYer, call your local HVAC technician to ensure you have clean gas furnace burners.

🛑 PRO TIP: Issues with furnace gas burners or heat exchangers can cause your furnace to leak carbon monoxide if not maintained correctly.

symptoms of carbon monoxide poisoning

Carbon monoxide in the right amounts can kill, so it’s best to have your furnace checked by an HVAC professional if you have any concerns.

Best Practices for Maintaining a Furnace Burner

phyxter hvac tech repairing a furnace

A great way to keep your HVAC system and, in particular, your furnace in good working order is to clean and service it regularly.

Given the complexity of furnaces and their associated systems, we always recommend that a yearly inspection and service is done by a qualified HVAC professional.

By being proactive, you can ensure the longevity of your HVAC system and keep your monthly energy costs low.

Small investments in preventative maintenance can go a long way in avoiding costly furnace repairs in the future.

How to Clean a Gas Furnace Burner?

As previously discussed, any servicing or repair should be conducted by an HVAC technician, but if you’re keen to carry out basic cleaning and servicing yourself, check out this quick guide:

PRO TIP: When carrying out any type of teardown of equipment, take photos at each step as a reminder of how it should look when you put it back together.

Yellow Furnace Burner Flame

🧰 The Blue Flame Test

Before switching off and disassembling your furnace for cleaning and servicing, you should carry out a blue flame test.

Turn on your furnace and set the thermostat to heat and the temperature higher than the current temperature in your home. This will ensure that your furnace fires up.

Next, you will want to check the color of the flames from the burners.

You can see this through the small inspection panel in front of the furnace.

If this window is too small, you can remove the front main access panel and watch the furnace burners work.

Be aware that your furnace will be fitted with a door switch.

For you to operate your furnace with the access panel off, tape down the switch to trick your furnace into thinking the access panel is still there.

All the flames should be of equal size and a consistent blue color.

If you see any other colors like yellow or green and even orange streaks in the flames, these are signs of incomplete combustion caused by dirty burners.

This will highlight problems that you are going to check as you work your way through this list.

Also, check any red lights or error codes on your furnace control board. Most furnaces have a diagnostic indicator built into them.

This indicates the functionality of the measuring systems within your furnace.

You can read more about it here: How to Tell if Your Furnace Control Board Is Bad


🧰 Switch off the Furnace

Like all equipment with moving parts that are fed by a flammable substance, it needs to be shut down correctly for it to be safe to work on.

First, find the power switch to your furnace.

Hint: it should be nearby. Since we are all about safety, find your circuit breaker panel and switch off the corresponding furnace breaker.

Finally, switch off the gas supply at the gas valve feeding the furnace.

Hint: That should be close by as well.

🧰 Remove the Access Panels

So we can have easy access to everything, including the furnace burners, we need to remove the access panels.

Take the tape off the previous door switch. We want to make sure the furnace is off.


🧰 Remove the Gas Burner Retaining Plate

Remove the screws or bolts that hold the retaining plate to the combustion chamber.

Check that these retaining screws aren’t holding down anything else, like a wire clamp.

Remember, this has to be put back together the same way you took it apart. We don’t want to introduce new problems.

🧰 Remove the Burners

As per the picture, burners are round and resemble trumpets.

Start with the burner closest to the gas valve, and pull forward to disengage the lock that retains the burner within the burner assembly and lift it out.

Be careful that you don’t interfere with other parts near the burners, such as the pilot light assembly and the hot surface ignitor if one is fitted.

These parts are fragile, and it’s common for homeowners to damage them in the burner cleaning process.

As you remove each burner, inspect for markings to ensure they return the same way.

Mark the top with a marker if not easily distinguishable.

🧰 Clean Each Burner

Clean the exterior of the burner using a small wire brush.

Remove the buildup collected around the end facing the combustion chamber.

Use compressed air to dislodge any carbon deposits or remaining gunk from your scrubbing with the wire brush.

🧰 Clean the Flame Sensor

Furnace Flame Ignitor

The attached flame sensor is a small rod with a ceramic base that’s mounted right behind the last burner.

This sensor frequently gets covered in soot, which can interfere with its ability to sense a flame.

Unscrew the hardware holding it in and disconnect the wire.

You can clean the rod with fine steel wool to remove the carbon. Reinstall once it’s clean and shiny.

Related Reading: How to Clean a Furnace Flame Sensor in 5 Easy Steps!

🧰 Replace the Burners

Going in the reverse order that you started, replace the burners one by one.

This is done by gently lowering the burner back into place until the tabs reengage and the burner is horizontal.

They should clip back into place easily, don’t force them if it feels it’s not going to fit. It’s easy to break something at this stage if you’re not careful.

🧰 Replace the Retaining Plate

Put the plate back in position the same way you took it out, and make sure the retaining screws are tight.

🧰 Test the Furnace

Keeping safety in mind, retest the furnace as per the blue flame test.

Don’t forget to tape down the access panel switches. If you still see coloration that’s not a consistent blue color, it’s time to call in the professionals.

Incomplete combustion means you have other problems, such as a cracked heat exchanger, which can pose a danger by releasing carbon monoxide while the furnace is in operation.

Test again once all the access panels have been put back.

furnace heat exchanger

🧰 Additional Cleaning and Inspection

Before replacing the access panels, be sure to vacuum in and around your furnace. Also, wipe down the heat exchanger.

It’s also a great time to check the blower fins on the blower fan attached to the blower motor and clean them by wiping or with compressed air.

Go ahead and replace the air filter while you are poking around in your indoor air handler.



Troubleshooting, cleaning, and fixing a furnace burner can be a complex task and is not for the average homeowner. If you are an experienced DIYer, then give it a go.

If you feel uncomfortable, call any of your local HVAC technicians to complete the job.

With regular maintenance, you can keep your family warm and your utility bills and future repair costs low, knowing you have a nice clean, and healthy furnace.

Want to learn more about your home’s heating system? Feel free to check out our other furnace articles!

Russell Jones

Russell, a native Australian and VP of Operations at Phyxter Home Services, is also part-owner of Vernon Air Conditioning, Plumbing, and Electrical Services. When he's not busy with work projects and renovations, Russell enjoys putting his vast knowledge of home improvement to good use by sharing his tips and tricks.

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Phyxter (pronounced Fix-ter) is a national home services brand specializing in Residential HVAC, Electrical and Plumbing solutions.

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