You may not realize it, but your furnace, the silent workhorse keeping your indoor air comfortable in winter, could become a fire hazard. While heating systems keep the home warm in colder months, improper maintenance could put your property and your family’s lives at risk. On a brighter note, you can proactively prevent such risks. A few straightforward precautions can make all the difference in keeping your family and your home safe this winter. Continue reading to learn about the common causes of furnace fires and how to prevent them.
What Causes Furnace Fires?
According to the National Fire Protection Association (NFPA), heating equipment, including furnaces, is the second leading cause of home fires, with nearly half of these incidents occurring in the winter months of December, January, and February. Take a look at what typically causes furnace fires.
Dirty Air Filters

If you don’t change your filters every one to three months, you may be putting your home at risk of a fire. The grime that builds up on filters from air circulating through vents is highly combustible. This is why it is critical to replace filters regularly.
Dirt and Dust
It may be hard to believe that something as small as dust and dirt particles can cause a fire, but these combustible items can contribute to a furnace fire. The most dangerous type of dirt and dust may be within the furnace filter. However, dirt on the exterior and trapped within the furnace components can also help fuel a furnace fire.
Combustibles Near the Furnace
Dust on the exterior of the furnace isn’t the only threat. Storing flammable items too closely to the furnace could start a fire or cause an explosion.
Worn Electrical Components
Another way a furnace may catch fire is if its electrical components are worn out. This problem may be most noticeable on older heating units. However, newer ones that aren’t properly configured or have wires exposed to the heating elements can become damaged and cause a fire.
Improper Gas Pressure
Whether too much or too little gas is distributed from a gas furnace, this can lead to issues that could cause a fire. Little pressure increases the likelihood of flame rollout, which can spew flames inside the furnace and around it. High pressure can also damage the furnace components and potentially lead to a fire.
Blocked or Cracked Heat Exchanger
A heat exchanger allows the heat generated in the chamber to spread throughout the home while containing hazardous gases, such as carbon monoxide, as the fire burns. These gases are redirected outside via the flue. If the exchanger is blocked or damaged, it could allow dangerous gases to mix with the heat, potentially sending them through the home’s vents. It could also start a fire.
What Happens When Your Furnace Catches on Fire
Many furnaces, particularly those fueled by gas or oil, operate with the use of fire. Your home and valuables are at risk when the fire from the furnace gets out of hand and starts to spread. While a fire spreading throughout the space where the furnace is located is the most common disaster from a furnace fire, here are a few more devastating effects of a furnace fire.
Carbon Monoxide Leak

Known as a silent killer, carbon monoxide is an invisible, odorless gas that may leak throughout your house. Such leaks may come directly from a running car in a garage. However, appliances such as furnaces can also leak carbon monoxide. A cracked heat exchanger is the most common way this gas may leak. Having a carbon monoxide detector in the room where the furnace is located is a way to detect this gas and shut it off in the event of an emergency.
Explosion
Fires and gas leaks aren’t the only threats from a faulty furnace. In worst-case scenarios, a furnace could cause an explosion. There are many reasons a furnace could explode. Here are the most common ones:
- A dirty or faulty ignition system.
- Improper installation.
- Blocked flues or malfunctioning components.
Ways to Minimize Furnace Fires
You can prepare your furnace for winter and prevent a fire by keeping the following tips in mind.
Change Air Filters Frequently
One of the simplest ways to avoid a furnace fire is to change your filter regularly. Most filters need to be changed every three months. You may need to change your filter once a month if you have pets in the home and multiple people reside in the home. It’s ideal to follow the manufacturer’s instructions on when to replace your furnace filter for best results.
Keep Dust at Bay
Throughout the year, especially when the furnace is not in use, considerable dust and dirt can accumulate in and around the furnace. Before using your furnace this winter, it’s a good idea to vacuum away any dirt that may be on the furnace’s components and wiring. Cleaning around the furnace is also a good idea.
Avoid Storing Combustibles Near Furnaces
If you’re furnace is located in a closet, attic, or a basement, you likely use the area for storage. Just be sure that your stored items aren’t too close to the furnace, since flammable items near the furnace could cause a fire or an explosion. It is best to keep combustible objects, such as paper or furniture, at least three feet away from your furnace. Other items you’ll want to keep away from the furnace include paint, boxes, rags, laundry baskets, and wood.
Ensure Airflow Isn’t Restricted
In addition to avoiding storing items near the furnace, it is also a good idea to keep the airflow from being restricted. Avoid blocking the vents and other components to minimize the risk of a fire or explosion.
Check For Dead Pests
Although this is not always easy to determine until the furnace is in use, it’s a good idea to check the furnace and its components for the presence of pests. Believe it or not, furry critters can cause a fire by blocking parts of the furnace.
Know Where the Emergency Shutoff Valve Is
Sometimes, preventing a fire isn’t possible, but keeping it from spreading is. Therefore, it is a good idea to know the location of the emergency shutoff valve for the furnace. This action will cut off the supply to the furnace in the event of an emergency, such as a gas leak or fire.
Observe the Flame
If you’ve ever handled a candle or some other item with a flame, you know that the flame can reveal a lot. A flame that moves quickly may indicate a strong gust of air is nearby. A flame that’s not too strong may signify that there isn’t enough oxygen. If you have a gas or oil furnace, you’ll want to observe the flame. If it is jumping wildly all over the place, a furnace flame rollout may be the cause. Such activity with the flame could cause it to shoot out flames and ignite an adjacent wall, potentially leading to a fire.
Examine Wiring
Bad wires could also cause a furnace fire. If they are frayed or melted, using the furnace could cause the cables to ignite and spark a fire. A rodent may have also chewed the wires, causing significant damage. Before using your furnace, it’s a good idea to inspect the wiring for damage. If damages are present, you will need to hire a technician to replace the wires or consider replacing the furnace.
Install a Carbon Monoxide Detector and Smoke Detector
If you don’t have a carbon monoxide detector in your home, now is the perfect time to get one. A faulty furnace may be leaking carbon monoxide. Since it is odorless and invisible, the only way to detect a leak is with a detector. A smoke detector will also help keep you safe by sensing any smoke the furnace may release.
Let Your Ears and Nose Be Your Guide
As you use your furnace, it’s a good idea to take a whiff of the air to make sure the furnace is not on fire. Some odors that come from a furnace, particularly when it is used after summer, are normal. There may be a slight burning odor that disappears after a few minutes. However, if the burning smell persists or the odor seems electrical, you should turn off the furnace and call a professional to determine the cause of the issue.
Another problem you’ll want to look out for is unusual noises coming from your furnace. Almost all appliances have a certain noise level, and furnaces are no exception. You’ll typically hear a low humming sound while the furnace is in use, as it cycles through its operation. However, banging, clicking, or high-pitched noises could be a sign that something is wrong with the furnace.
Schedule Regular Maintenance

Before using your furnace for the winter, it is ideal to call on the experts for furnace maintenance. A professional may check the safety controls, clean the burners, inspect for carbon monoxide leaks, test the electrical connections, ensure proper airflow and venting, and replace the filter if necessary.

