Uh Oh! Why Is The Furnace Flame Yellow, Not Blue?

3 February 2017
 Categories: , Blog


One important part of furnace maintenance -- or more accurately, monitoring your furnace's performance -- is checking the color of the flame from time to time. Your furnace flame should be blue, sometimes with some specs of white thrown in. If the flame is yellow or orange, or a combination of blue with yellow or orange, then something is wrong. Here's a look at the likely causes and what you should do.

What causes a yellow flame?

The flame is yellow because it is not burning as hot as it should be. Blue and white fire are hotter than yellow or orange fire. There are a number of possible reasons why the flame may be too cool. The most likely cause is that the burner is dirty, prohibiting gas from combusting completely. One of the gas lines feeding into the burner may also be blocked or clogged, reducing gas flow.

What should you do about the yellow flame?

Both clogged gas lines and a dirty burner are issues that should be addressed by a professional. If you don't perform the necessary maintenance very carefully, there's a risk of injuries and gas explosions. So when you notice a yellow flame, the first thing you should do is call an HVAC repair specialist.

Next, take stock of your carbon monoxide detector. Make sure that you have one and that the battery is working. Incomplete gas combustion, which is common with a yellow flame, can cause carbon monoxide to be generated and to leak into your home. This is not something to take lightly, since CO poisoning can be deadly. If the detector goes off, find somewhere else to stay until the HVAC repair specialist arrives.

How will your repair person fix the problem?

Cleaning the burner or unclogging a gas line should only take your HVAC specialist an hour or two. He or she will use special tools to remove soot from the burner or to scrape debris from the inside of the gas line. Once this task is complete, the flame should burn a nice, hot blue again. You'll notice that your home warms up a lot faster and that your energy bills go down.

Put checking the color of your furnace flame on your once-a-month checklist. This way, if your furnace does develop a problem with the burner or gas lines, you know that it will be detected and treated early on. For more information, contact a heating contractor at a company like Erickson Plumbing & Heating.