Why Your Furnace Has a Strange Smell

As the weather gets colder and you swap from cooling to heating your home, you may be worried about unusual furnace smells in the air. Learn about what the most common furnace smells mean and how proactive you should be about them.

The Furnace Smells Musty

Musty furnace smells generally indicate mold growth someplace in the HVAC system. To avoid exposing your family to allergy-inducing mold, tackle this problem right away.

A clogged air filter can harbor mold, so eliminating the smell might be as straightforward as swapping out filter. If that fails to remove the smell, the AC evaporator coil placed near the furnace may be the culprit. This component accumulates condensation, which could induce mold growth. You'll be better off with a professional’s help to check and clean the evaporator coil. When this still doesn't help, take a look at scheduling air duct cleaning. This service cleans away hidden mold, regardless of where it’s growing in your ductwork.

The Furnace Smells Like Spoiled Eggs

This is one of the most nerve-wracking furnace smells because it probably suggests a gas leak. The utility company puts in a special substance called mercaptan to the natural gas supply to make leaks easier to detect.

If you detect a rotten egg smell around your furnace or coming from your air ducts, switch off the heater immediately. If you can find where the main gas supply valve is located, shut that off also. Then, leave the house and call 911, as well as your gas company. Don’t go back in the house until a professional confirms it’s safe.

The Furnace Has a Sour Stench

If you detect a sour smell that stings your nose while standing near the furnace, this could mean the heat exchanger has cracked. This vital component houses combustion fumes, like carbon monoxide, so a crack may pump unsafe levels of CO gas into your home.

Carbon monoxide poisoning can be deadly, so turn 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 the culprit. For your health and safety going forward, make sure you have reliable CO detectors on every floor of your home.

The Furnace Smells Dusty

When you start the furnace for the first time every fall, you should expect a dusty odor to show up for a brief moment. This is the smell of six months’ worth of dust burning away as the furnace wakes from its summer slumber. As long as the smell disperses within one day, you shouldn't have anything 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 clogged, and now fumes are flowing back into your home. The odor might eventually reach the entire house, risking your family’s health if you neglect it. So turn off the furnace and contact a professional straightaway to schedule a repair.

The Furnace Smell Resembles Burning Plastic

Overheating and burned electrical components are the most plausible reason for a burning plastic smell to make an appearance. A failing fan motor is another common cause. If you don’t tackle the problem, an electrical fire might start, or your furnace could experience irreparable damage. Disable the heating system as soon as possible and call an HVAC technician for help troubleshooting and repairing this weird furnace smell.

The Furnace Has an Oily Smell

If you own an oil furnace, you might detect this stench whenever the oil filter becomes blocked up. Try replacing it to determine if that resolves the problem. If the smell lingers for more than 24 hours after taking care of this step, it might indicate an oil leak. You'll be better off with help from an HVAC expert to address this problem.

The Furnace Reeks of Sewer Odors

Sewer gas smells pretty similar to spoiled eggs, so first eliminate the possibility of a natural gas leak. If that’s not the problem, the sewer lines might have an issue, for example a dry trap or sewer leak. Flush water down the drains, including the basement floor drain, to fill dried-out sewer traps. If the smell sticks around, you should contact a sewer line repair company.

Contact San Antonio Air Service Experts for Furnace Repair

If you're still unsure, call an HVAC technician to examine and repair your furnace. At San Antonio Air Service Experts, we deliver complete diagnostic services to identify the problem before repairs begin. Then, we encourage 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 problem, and we back our work with a 100% satisfaction guarantee for one year. To ask questions about why your furnace smells bad or to request furnace repair near you, please contact your local San Antonio Air Service Experts office today.

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