Can Furnaces Catch Fire?

The return of cold temperatures increases your reliance on home heating equipment in the fall. If your furnace isn’t functioning correctly, it may develop into a fire hazard and jeopardize your family’s safety. 

As stated by the National Fire Protection Association (NFPA), heating systems like furnaces are a major cause of home fires, leading to almost 50,000 blazes, 500 civilian deaths and more than $1 billion in significant property damage each year. Space heaters and fireplaces generate most of the fires affecting heating equipment, but central heaters, like furnaces, are accountable for just about 12% of these blazes. Learn the leading causes of furnace fires and how to minimize them. 

Causes of Furnace Fires

Aging furnaces are more vulnerable to safety hazards as they might be configured differently and slide into disrepair through the years. That being said, whether your furnace is more than a decade old or brand new, you should be aware of these causes of furnace fires. 

Overheating Motor

A furnace motor can overheat in various ways. Here are the most common risks:  

  • A clogged filter can restrict airflow and cause the motor to work harder. Sooner or later, the motor may overheat, raising the risk of fire. 
  • Dirt can accumulate around and cover up the motor, forcing it to absorb heat, which can cause a fire. 
  • Exposed or deteriorated wiring can cause the voltage to get too high, increasing the chances of an electrical fire. 
  • Excessively tight or damaged motor bearings can heat up when the furnace starts. Without adequate lubrication, the bearings could eventually light on fire. 

Obstructed Furnace Flue 

Yard debris, animal nests and other materials can obstruct the furnace flue, reducing oxygen. This causes soot building up and improper ventilation, decreasing efficiency and raising the risk of flame rollout. Flame rollout is when fire reaches past the heat exchanger and burns the parts inside your furnace. If this problem persists, your heating equipment could be severely damaged, and the fire may even spread to areas outside the furnace. 

Clogged Heat Exchanger 

The heat exchanger is a restricted combustion chamber where the heat generated by your furnace is exchanged to the air circulating within your home. A heat exchanger blocked with soot or corrosion has the same effect as a blocked furnace flue—reduced performance and a higher risk of flame rollout. 

Cracked Heat Exchanger 

Various problems occur if corrosion breaks the heat exchanger. First, it reduces suction in this chamber, resulting in less airflow and increased flame rollout. Second, it releases fumes, including carbon monoxide, into your home. Breathing in CO gas can be lethal, so never ignore your carbon monoxide alarms. CO gas can also flash back to the source of the leak and ignite if a flame is lit. 

Improper Gas Pressure 

Furnaces depend on a precise combination of natural gas and air to produce safe and efficient combustion. Too little pressure is often the result of clogged burner orifices. This problem makes the burner flames more likely to roll out. It also causes unwanted condensation inside the heat exchanger, accelerating the rate of corrosion. 

On the other hand, high gas pressure can create excessive heat within the furnace, which can cause the soot inside the heat exchanger to combust. Such fires can quickly spread to other areas. 

How to Prevent Furnace Fires 

Based on the various ways a furnace can light on fire, here are the steps you can take to prevent furnace fires: 

  • Change the air filter on a regular basis: Check the filter each month and change it when it looks dirty or every three months, whichever comes first. 
  • Check the furnace flue: Periodically check the exterior vent for obstructions and take care of any you find. 
  • Don’t store combustible items near the furnace: Things like cardboard boxes, paper, clothing and other combustibles should be kept at a minimum 3 feet away from the furnace and all other heating equipment. 
  • Install a flame rollout switch: This safety component detects if a fire or hot exhaust gases are inside your furnace’s burner compartment. If the rollout switch trips, have your furnace inspected right away to diagnose and repair the problem before it results in a furnace fire. 
  • Schedule annual furnace maintenance: It isn’t always easy to recognize if your furnace is performing unsafely. Whether you notice warning signs or not, remember furnace maintenance every fall. 

Schedule Furnace Services Today 

Is it time for your annual tune-up? Do you need help resolving a problem with your furnace? Whatever the reason, Service Experts Heating, Air Conditioning & Plumbing is here for you. Our HVAC pros can inspect, clean and test the system to provide safe operation. If anything doesn’t seem right, we’ll suggest a repair or a modification, offering you peace of mind that your furnace is unlikely to catch fire. For more information or to schedule furnace maintenance, please contact your local Service Experts Heating, Air Conditioning & Plumbing office today.