What Color Should Your Furnace Flame Be?

One helpful tip that most HVAC installation companies would share with you is that the color of your furnace flame can be a good indicator of the fuel efficiency of your heating system. You can tell that your furnace is in great working condition if it emits a blue flame with a blue triangle at the center.

So if furnace flames are colored yellow or orange, what does this tell you? There are different indicators that correspond to different flame colors, and it’s important to know what they all mean. This is because these colors indicate that your furnace isn’t burning fuel efficiently and needs to be thoroughly inspected by a local HVAC professional.

In this post, Cafco Services, one of the top local heating and air conditioning maintenance companies, shares a comprehensive guide on flame colors and the corresponding meanings.

Furnace Flame Colors & What Affects Them

The color of furnace flames will vary depending on the amount of oxygen being burned by your furnace. The flame gets hotter proportional to the oxygen driven by the furnace. Ideally, oxygenated flames are colored blue, and they burn thoroughly without byproducts like soot. Some homeowners might think that yellow or red flames are normal, but these colors actually indicate that your furnace isn’t getting much oxygen, as with a candle flame.

HVAC installation companies will tell you that blue flames indicate an oil or gas furnace in optimal condition. Any other color will tell you that there’s a problem with your furnace unit. In addition to producing more soot than normal, partial combustion also produces toxic substances like carbon monoxide (CO), which can cause dizziness, respiratory issues, headaches, and in serious cases, even death. Here’s a quick recap of what different flame colors mean:

• Blue flames. Blue flames are the hottest that your furnace can produce. They can give off high amounts of heat since the process is completed with efficient combustion.

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• Yellow flames. HVAC repair companies will tell you that yellow flames signal the production of carbon monoxide. CO is known as an odorless, colorless, tasteless gas that can cause nausea, headaches, respiratory issues and even death. This means that your furnace is combusting fuel inefficiently.

• Yellow and orange flames. The cause of these colors is similar to that of yellow flames, except yellow and orange flames emit the least amount of heat, causing inefficient furnace operation.

What Should Your Furnace Flame Color Be?

Ideally, your natural gas furnace should emit flames that are either blue or almost completely blue. HVAC repair companies will tell you that a furnace emitting raging blue flames with light blue triangles at the center indicate optimal furnace operation. It’s okay if there are small hints of yellow. Blue flames tell you that the gas is being used in a safe, efficient manner, with little to no waste. The bluer the furnace flames get, the hotter they are, and the more efficient the combustion.

Additionally, blue flames indicate that the gas being burned is clean, burning the fuel completely and leaving only traces of contaminants or moisture. To ensure that your furnace has complete combustion, there needs to be a stable supply of oxygen.

Complete combustion can be achieved when there are blue flames present. When your furnace fuel burns efficiently, it emits the most heat and remains energy-efficient without wasting too much energy during heat production. If you notice your flames turning orange or yellow, have them inspected so that you can repair or replace your furnace as soon as possible.

What Causes Red, Yellow or Orange Flames?

The color of the flames is determined by two key factors: the fuel composition and the flames’ temperature. Your HVAC contractor will tell you that pure hydrocarbons like natural gas or propane will definitely create blue flames. Other materials that contain chemicals or compounds won’t burn blue. The most prevalent colors are red, orange and yellow, with the main color indicating how hot the flame is burning.

You might wonder what causes the furnace flame to be anything other than blue. This is actually due to dirt in the furnace, gas pollutants or moisture in the gas.

Try to use treated wood in a fireplace or campfire. Since there are traces of sodium within firewood, it will usually burn a bright orange. Keep in mind that pine and other coniferous trees contain a lot of turpentine and resins, making them burn quicker, producing a yellow flame. However, if you’re using natural gas or propane, anything other than a blue flame indicates that you have a furnace problem. Make sure to get your furnace checked by your local furnace installation contractor.

How Can You Ensure Proper Combustion?

When you operate your furnace for the first time during the winter season, pay close attention to the flame colors. Turn off your furnace immediately if the flame isn’t lighting up blue. Afterward, you should call your furnace technician for further assistance. Issues can be further prevented by following a routine maintenance and inspection schedule, which is why it’s important to have your furnace checked during the fall months. 

You can add an extra layer of protection for your family by installing a carbon monoxide detector at key points around your house, like the living room, kitchen and bedroom. These alarms will go off when they detect dangerous levels of carbon monoxide. It’s also important to check your HVAC air filter for contaminants like dust, debris and soot, and have it replaced immediately. When your furnace burns blue, this simply means that your furnace is operating safely and at optimal levels. In addition to safety concerns, operating a faulty furnace will also harm your home’s energy efficiency.

Make your search for heating and air conditioning maintenance companies easier by turning to Cafco Services. When it comes to residential and commercial HVAC services, we’re the number one professionals to approach, and we won’t let you down! Give us a call at (513) 242-3400 or fill out our contact form to schedule an appointment.