Everything You Need to Know About Furnace Fires

By: Diana Rodriguez-Zaba
Updated on: March 25, 2024

That crisp, cold air means it’s time to get ready for chilly weather. You look forward to snuggling in and spending warm evenings at home. You count on the furnace to keep the cold at bay, but are you sure it’s ready to operate safely through the long months ahead?

We help Chicago homeowners recover from damage caused by furnace fires every winter. That’s why we’ve developed this overview of important facts you need to know about your home’s furnace.

Let’s start now.

What Causes Furnace fires?

furnace fire

The furnace sits quietly for months, so your DIY fall furnace routine includes inspection by an HVAC pro. Still, problems can develop and lead to a dangerous situation.

These are four common causes of furnace fires:

1. Blocked Air Filter

A dirty furnace filter compromises equipment performance and efficiency. It interferes with air flow and allows airborne contaminants into the system. The furnace works harder and overheats. Extreme temperatures can result in the motor catching fire.

2. High Gas Pressure

When a gas furnace works properly, it combines a balanced mixture of gas and oxygen to produce safe, steady heat. This takes place inside the combustion chamber at a pressure specific to the furnace model. Too much pressure causes excessive temperatures and flammable soot buildup inside the heat exchanger.

3. Carbon Monoxide Leaks

Furnaces that burn combustible fuel generate carbon monoxide. As long as the equipment operates correctly, the highly flammable gas vents outside the home through the furnace flue. Cracked or damaged components can result in leaks that allow carbon monoxide to accumulate inside the furnace and burst into flames.

4. Overheated Motor Components

When furnace parts overheat, they pose a serious fire risk. Common problems include bad wiring, excessive voltage, dry motor bearings and restricted air flow. Any of these conditions can create excessive heat in the motor, and that can start a furnace fire.

What Causes Flame Rollout?

Flame rollout is a very dangerous event that can occur during a furnace fire. It’s best described as fire coming out of the furnace. When inflammable gases build up inside the furnace, their presence starves the flames of oxygen.

As the fire seeks more fuel, it escapes the combustion chamber and rolls flames over nearby materials. Discoloration and singeing on the chamber’s exterior are sure signs of a flame rollout. If you notice this type of damage, turn off the furnace, and call your HVAC professional right away.

5 Warning Signs Your Furnace Is Going to Explode

Furnace explosions don’t happen often, but the results can be devastating. There are DIY steps for troubleshooting your home’s furnace, but call an HVAC technician if you notice any of these potentially serious signs.

1. Loud noises inside the furnace, such as banging, popping and rattling, are usually caused by component failure.

2. A yellow burner flame is normal, but a blue flame indicates the presence of highly explosive carbon monoxide.

3. Foul odors coming from the heater are signs that the internal combustion process isn’t operating properly.

4. Streaks of soot on the exterior of the furnace flue or chimney are caused by dangerous overheating inside the unit.

5. A tripped carbon monoxide detector indicates furnace problems that must be taken care of immediately.

Can an Electric Furnace Catch on Fire?

Most furnace fires occur in models powered by combustion. However, electric furnaces can also pose a home fire risk. Faulty wiring or bad connections can lead to sparking. This can ignite materials near the furnace and start a fire that quickly spreads through the house.

How to Put Out a Furnace Fire

Heating equipment is the second leading cause of house fires. Most of these incidents involve small appliances, and the fires can usually be contained without too much damage.

Trying to put out a furnace fire by yourself can be very risky. The size and location of the unit make it dangerous. If your furnace catches fire, don’t take chances. Immediately evacuate your home, and call 911. If you’re able to, use a dry chemical fire extinguisher (carbon dioxide) to try to put out the flames.

How to Prevent Furnace Fires

furnace fire safety

Preventing a furnace fire starts with regular DIY maintenance and an inspection by a licensed HVAC technician. It’s important to keep the unit clean too. Change filters often, don’t let dust accumulate around the unit, and have the duct work cleaned once a year. Consider installing a rollout safety switch on your furnace.

Depending on equipment type, follow these furnace fire safety tips to lower the risk of a furnace fire spreading through your home.

Gas Furnaces

  • Keep stored materials at least 3 feet away from the furnace.
  • Make sure snow on the roof doesn’t block exterior furnace vents.
  • Install a carbon monoxide detector in each level of the house.
  • Locate and know how to operate the gas supply shutoff valve.

Oil Furnaces

  • Regularly clean the furnace pump strainer to avoid blockages.
  • Routinely check and clean the stack control safety mechanism.
  • Make sure nothing blocks the furnace registers.
  • If you see black smoke coming from the flue or chimney, call your HVAC pro.

Electric Furnaces

  • Don’t try to DIY install humidifier or air purification systems in HVAC equipment.
  • Call an HVAC professional if you see frayed wires or damaged connections.
  • Be prepared to shut down your home’s electricity supply in case of a fire.

Alternative Fuel Furnaces

  • Always use well-cured wood in wood-fueled furnaces.
  • Stay safe by installing carbon monoxide detectors throughout the house.
  • Have the furnace flue or chimney professionally cleaned at least once every season.

Dealing With the Aftermath of a Furnace Fire in Chicago, IL or Suburbs? We Can Help!

We hope everyone across the city enjoys a safe, warm winter this year. If you should face the damages cause by a furnace fire, you can count on us. For more than 10 years, we’ve provided industry-certified fire damage recovery for Chicago home and business owners.

ServiceMaster by Zaba stands ready to answer your call 24/7, and we’re just around the corner: 773-647-1985.