Why Your Furnace Has a Strange Smell

As the weather gets colder and you swap from cooling to heating your home, you might be worried about weird furnace smells filling the air. Learn what the most common furnace smells mean and how concerned you should be about each one. 

The Furnace Smells Musty 

Musty furnace odors usually indicate mold growth somewhere in the HVAC system. To avoid subjecting your family to allergy-inducing mold, handle this problem as soon as possible. 

A damp air filter can harbor mold, so eliminating the smell could be as easy as replacing the filter. If that doesn’t work, the AC evaporator coil fastened near the furnace could be to blame. This component collects condensation, which will sometimes trigger mold growth. You’ll want a professional’s help to examine and clean the evaporator coil. When all else fails, consider investing in air duct cleaning. This service removes hidden mold, no matter where it’s growing in your ventilation. 

The Furnace Smells Like Rotten Eggs 

This is one of the most nerve-wracking furnace smells because it most likely suggests a gas leak. The utility company adds a useful substance known as mercaptan to the natural gas supply to make leaks easier to detect. 

If you notice a rotten egg smell around your furnace or coming from your vents, shut off the heater immediately. If you know where the main gas supply valve is, shut that off too. Then, leave the house and call 911, followed by your gas company. Don’t go back in the house until a professional tells you it’s safe. 

The Furnace Has a Sour Stench 

If you detect a sour smell that stings your nose while standing close to64} the furnace, this could mean the heat exchanger has cracked. This essential component safely contains68} combustion fumes, including carbon monoxide, so cracks could pump unsafe levels of CO gas into your home. 

Carbon monoxide poisoning can be deadly, so shut off your furnace right away if you detect a sour odor. Then, contact an HVAC professional for an inspection. Consider replacing your furnace if a cracked heat exchanger is to blame. For your health and safety going forward, make sure you have working CO detectors on every floor of your home. 

The Furnace Smells Dusty 

When you start the furnace for the first time every fall, you can expect a dusty odor to appear for a brief moment. This is the smell of six months’ worth of dust burning off as the furnace wakes from its summer slumber. As long as the smell disperses within one day, you have nothing to worry about. 

The Furnace Has a Smoky Smell 

Natural gas, oil and propane furnaces are combustion appliances, so they vent fumes to the exterior. A smoky smell could mean the flue is backed up, and now fumes are backdrafting into your home. The odor may permeate the entire house, endangering your family’s health if you neglect it. So switch off the furnace and call a professional right away to arrange for repair. 

The Furnace Smell Resembles Burning Plastic 

Overheating and melting electrical components are the most plausible reason for a burning plastic smell to come from your furnace. A failing fan motor is another possibility. If you don’t tackle the problem, an electrical fire could start, or your furnace could experience irreparable damage. Turn off the heating system immediately and call an HVAC technician for help troubleshooting and repairing this weird furnace smell. 

The Furnace Has an Oily Smell 

If you use an oil furnace, you might detect this odor when the oil filter becomes clogged. Try replacing it to see if that fixes the problem. If the smell lingers for more than a day after taking care of this step, it could indicate an oil leak. You should get help from an HVAC expert to fix this problem. 

The Furnace Reeks of Sewer Odors 

Sewer gas smells quite similar to rotten eggs, so first rule out the potential for a natural gas leak. If that’s not the problem, your sewer lines could have an issue, such as a dry trap or sewer leak. Try pouring water down all your drains, including the basement floor drain, to refresh dried-out sewer traps. If the smell sticks around, you’ll need to contact a sewer line repair company. 

Contact Stevenson Service Experts for Furnace Repair 

When in doubt, get in touch with an HVAC technician to check and repair your furnace. At Stevenson Service Experts, we perform thorough diagnostic services to pinpoint the problem before the work begins. Then, we suggest the most viable, cost-effective repairs, as well as an up-front estimate for every option. Our ACE-certified technicians can resolve just about any heating repair, and we back our work with a 100% satisfaction guarantee for one year. For details about why your furnace smells bad or to request furnace repair near you, please contact your local Stevenson Service Experts office today.