Here’s a useful energy-saving tip: the color of your furnace flame is an indicator of the fuel efficiency of your heating system. Your furnace is in good working order if it has blue flames with a light blue triangle at its center. 

What are the meanings of the various flame colors? What if the flame in the furnace is yellow or orange in color?  Colors other than blue are a symptom that your furnace’s fuel combustion is inefficient and your heating system in general needs to be evaluated by a professional HVAC specialist.

Here Bill Reynolds Heating & Air Conditioning, your go-to air conditioning repair company, offers a quick primer on furnace flame colors and what they indicate.

Furnace Flame Colors

The color of the flame changes depending on how much oxygen is burned. The flame gets hotter as the oxygen supply increases. This produces a blue-colored flame that burns more thoroughly and produces less waste material like soot. The flame color changes from red to yellow when it doesn’t get enough oxygen, as occurs with a candle flame.

A blue flame signifies a properly-functioning oil or gas furnace; any other color indicates a problem with the furnace. In addition to producing more soot, incomplete combustion produces more carbon monoxide (CO), which can cause headaches, nausea and even death if inhaled in large quantities.

• Blue flames are hotter than other flame colors because they’re created by complete or efficient combustion.

• Yellow flames signify the generation of carbon monoxide, an odorless, colorless, tasteless gas that can produce headaches, nausea, hallucinations and, in severe cases, blackouts, in addition to being a symptom of inefficient combustion.

• Yellow and orange flames provide the least amount of heat.

What Color Should a Furnace Flame Be?

Your natural gas furnace’s burner flames should be almost totally blue. The sign of a good natural gas furnace, according to heating service professionals, is a roaring blue flame with a light blue triangle in the center. A sliver of yellow may also be present. A blue flame signifies that the gas is being used safely and efficiently, rather than being wasted. The bluer the flame, the hotter it is, and the more complete the combustion.

A blue flame shows that the gas is clean, with few contaminants and minimal moisture. For complete, blue combustion, there must be an adequate supply of oxygen.

Complete combustion is indicated by a blue flame. When your furnace burns completely, it produces the most heat and uses less energy to provide the proper amount of heat. Incomplete combustion can easily be detected, and the furnace should be changed as soon as possible if this is the case.

What Causes a Red, Orange or Yellow Flame?

A flame’s color is determined by two factors: the composition of the fuel being burned (what it is and what’s in it) and the temperature of the flame. According to air conditioning repair professionals, pure hydrocarbons such as natural or propane gas burn with a blue flame. Many other materials that burn are made up of different chemicals and compounds that don’t turn blue. Red, orange and yellow are the most prevalent additional flame colors, with the main color also serving as a temperature indicator.

What causes the furnace flame to be orange, yellow or red? Is it possible for it to be another color, such as green? The main causes of other colors are dirt in the furnace and pollutants or water in the gas.

Consider wood in a fireplace or campfire. Because sodium is present, it usually burns a bright orange color. Pine and other coniferous trees contain a lot of turpentine and resins, so they burn hot and fast, producing a flame that’s more yellow than orange. Oaks and other hardwoods are more difficult to light and burn more slowly, producing an orange flame that’s not as fierce as pine but lasts longer.

When it comes to natural gas and propane, any color other than blue indicates an issue that requires the attention of a furnace installation specialist.

What’s the Danger of the Wrong Flame Colors?

A blue flame from your furnace or gas stove indicates that the gas has become completely combustible. If your burner flame is yellow, orange or red, this usually indicates that it’s not receiving enough air for complete combustion.

In addition to wasting gas, increasing energy bills and producing more soot, the primary concern associated with inefficient combustion is the increased amount of carbon monoxide (CO) created during the combustion process.

Carbon monoxide, dubbed the “silent killer,” is an odorless, colorless, tasteless gas that can cause headaches, nausea, hallucinations and, worst-case scenario, even death. Many people describe carbon monoxide poisoning symptoms as flu-like.

Due to the seriousness of carbon monoxide poisoning, heating service professionals strongly recommend installing CO detectors on each level of your home and outside each bedroom.

What Can You Do to Ensure Proper Combustion?

When you turn on your furnace for the first time of the season, pay attention to the flame colors. You should stop using your furnace immediately if the flame color is anything other than blue and call a heating and air conditioning repair technician for help. By adhering to a regular maintenance schedule, you lessen the chance of an emergency occurring. Before the heating season begins, it’s essential to perform winter maintenance.

Keep your family safe by installing carbon monoxide (CO) detectors around the house. When installed in bedrooms, these low-cost alarms sound if they detect CO levels above a predetermined level. If your HVAC air filter becomes clogged with indoor air contaminants such as soot, you should replace it immediately.

In conclusion, blue flames signal the safe, efficient operation of your gas appliance. If you discover that your gas flame isn’t blue, turn off the device and contact a service specialist. You’ll save money and be much safer with a blue flame.

At Bill Reynolds Heating & Air Conditioning, our top-rated technicians will take the stress out of the process and find a solution that meets your home’s needs and works with your budget. In addition to AC maintenance and repair services, we also provide furnace installation, indoor air quality checks and duct cleaning and sealing.

Give us a call at (440) 298-4698 or fill out our contact form to request a quote or schedule a service appointment.