No one wants their furnace to go out in the middle of winter, but there is one thing worse than a furnace that stops working — a furnace that puts your home and family in jeopardy. Knowing the symptoms of dangerous problems with your heating system ensures you know when to call for professional help.

Foul odors

When you first fire up your furnace at the start of the heating season, you sometimes get a light scorch scent through the vents for the first cycle or two. This is typically the odor of the dust burning off the heating elements and blower inside the furnace. If the odor persists for more than a day, or if it has a smell best described as burning metal, then you need to shut off the furnace and call an HVAC service. Burnt metal or persistent scorch odors can indicate an issue with the electrical wiring, which can lead to an electrical fire if not repaired.

For gas furnaces, your main concern is the odor of sulfur or rotten eggs. This odor indicates a gas leak, which if it ignites, can lead to an explosion in your home. If you smell this odor, leave the home immediately and call emergency services. Do not make the call from inside the house, and do not turn on or turn off any lights or other fixtures. These actions can result in a small spark, which can ignite the leaking gas.

Carbon monoxide

Arguably, one of the most deadly problems a furnace can present is carbon monoxide. This deadly gas is an odorless and silent killer, which leads to a slow death by asphyxiation. The best way to avoid this threat is to have carbon monoxide detectors installed throughout your home. Fortunately, many smoke detectors are now combination carbon monoxide detectors as well. Place these detectors near the furnace as well as in or near the bedrooms in your home. Check them monthly to make sure they are operating correctly. If a detector goes off, turn off the furnace until you can have it serviced.

Failing pilot light

Pilot lights are a small flame that ignites the gas to make a gas furnace operate. A light that won't stay lit or that flickers when lit can pose a hazard, since this may indicate an obstructed gas valve or uneven gas flow. Both can pose a fire hazard. If you have any issues or suspect any issues with a pilot light, call a service technician for an inspection and repair visit.