During the first few furnace heating cycles each fall, many homeowners notice a burning smell wafting through the house. This and other unpleasant aromas are attributed to different sources within your heating system. To help determine the cause of the odor problem, read below about the most common causes of a smelly furnace.
Why Does My Furnace Smell Funny?
1. Burning Smell
During the warmer months when your furnace sits idle or is cooling your home in conjunction with your air conditioner, fine particles of dust accumulate on the heat exchanger. The heat exchanger is the part of the furnace that is heated up by the burning of natural gas or propane. The heat exchanger can get hot enough to burn off these small particles of dust (without causing a fire hazard, thankfully), and it creates a faint burning smell that may persist for the first few heating cycles each heating season. After that, the odor disappears until … next fall.
2. Musty Odor
If a musty odor is produced by your furnace, it is often caused by excessive moisture. Most often, these problems are found in systems that sit idle for long periods of time and are in areas of high humidity. Basements or crawl spaces with dirt floors or exposed earth are especially problematic and may call for the installation of a quality dehumidifier and cleaning of the ductwork system to fully remove the musty smell.
3. Rotten Eggs
As a safety precaution, suppliers of natural gas and propane gas add a gas called Mercaptan to their natural and propane gas products. It has a distinctive rotten egg or sulfur smell. If you detect the stench of rotten eggs, take action immediately! The odor is meant to alert you that there’s a problem with the furnace. Reach out to a furnace repair technician or your gas supplier for advice on how to proceed with repairs. Be aware that if either your gas lines or furnace is determined to be leaking gas, the HVAC or gas company technician will disable your furnace and/or turn off the gas to your home as a safety precaution. Resist the urge to turn the gas back on after the tech leaves, because the leaking gas can produce life-threatening consequences. Once repairs are completed by a qualified technician, gas service will be fully restored to your home.
4. Burning Plastic
The presence of a burning plastic smell is usually an indication of an overheated wire or an electronic component failure. Wires providing power to fan motors and circuit boards are typical culprits, and an HVAC technician should be contacted to diagnose the source as soon as possible and make the appropriate repairs.
5. Metallic Odors
If the odor smells like burnt metal, your system is likely experiencing a short circuit. Corroded wires or wires with damaged insulation can contact surrounding metal parts creating a dangerous arcing condition. These wires could overheat and short circuit. Your best response would be to reach out to a professional to identify and fix the problem.
6. Carbon Monoxide
You cannot smell carbon monoxide, which makes it especially dangerous. This is why fire departments and safety experts around the world recommend that each home have a carbon monoxide detector to supplement their smoke detector. If carbon monoxide is making its way into your living space, that normally indicates a venting problem or a cracked heat exchanger. HVAC technicians can test for this colorless, odorless gas each year while performing the annual, preventative maintenance of your heating system.
If you’ve noticed a burning smell coming from your furnace, contact Jon’s Plumbing & Heating in Mount Vernon. Our trained technicians perform heating and cooling maintenance and repair to improve the comfort and efficiency of homes throughout the Knox County area. Read client feedback, and call (740) 392-5667 for a service estimate.