Furnaces are among the most common types of heating systems in the United States. According to the U.S. Energy Information Administration (EIA), around 118 million homes use some type of furnace to maintain comfortable indoor temperatures during cold seasons. Furnaces heat air inside a system and then distribute the heated air through ducts so that it can reach each room in your living space. But if your furnace begins to emit strange odors, it is a sign of a serious problem. A look at the types and causes of unusual furnace smells can help you understand what is happening with your system and know what actions to take.

Dusty Furnace Smell

Dusty smells are among the most common odors that emerge when homeowners turn on their furnaces for the first time of the season. When a furnace sits dormant during the warmer months of spring and summer, the appliance can collect dust. Upon powering the furnace back on once the weather cools down, this dust may singe and cause a slight smell throughout the home. This occurrence is normal and often wears off within the first 24 hours of use. If the smell persists longer than a day or so, contact an HVAC professional to investigate and repair the problem.

Smoky Furnace Smell

Smoke is another smell that requires expert intervention. A furnace that produces a smoky or sooty scent can indicate a blockage or an obstructed chimney. If smoke cannot leave the chimney or flue pipe as intended, the smoke will drift back down through furnace ducts and seep into various rooms. An HVAC technician can help you temporarily turn off the gas line and clear out any blockages to eliminate this unpleasant odor. Unaddressed blockages can cause fire hazards, so it is important to have these obstructions removed right away.

Rotten Eggs Smell

The rotten egg smell can indicate natural gas leaks and high concentrations of carbon monoxide (CO). Because natural gas has no odor of its own, many gas companies add a chemical called mercaptan to help warn occupants when gas leaks have occurred. This sulfur-based substance has a distinctive smell that most people compare to rotten eggs. Prolonged exposure to natural gas can lead to carbon monoxide poisoning.

This poisoning may produce symptoms such as headaches, dizziness, nausea, fatigue, or irregular breathing. Before long, carbon monoxide poisoning can quickly lead to a medical emergency and result in permanent injury or death. To avoid health problems, you should evacuate the home and contact a professional for repairs. Do not reenter the vicinity until an expert verifies that the issue has been resolved.

Musty Furnace Smell

Musty furnace smells result from a buildup of moisture within your system. The accumulation of moisture creates the perfect breeding ground for mold, mildew, or algae within ducts or along coils. When your furnace is burning this organic material while running, it can produce a musty scent. Because exposure to mold spores can lead to respiratory problems, it is important to contact a technician to identify the source of the moisture and complete repairs. For example, an expert can determine whether loose hose connections or leaky pipes have produced excess moisture. If the air within your home is too damp, a technician can also offer solutions, such as installing a dehumidifier to reduce the air’s moisture content and increase overall home comfort.

Oily Furnace Smell

Oily furnace scents have several potential causes. For one, this odor can indicate a clogged furnace filter. Contact an HVAC company for proper filter replacement. An HVAC professional may also suggest a filter upgrade with a better MERV rating to promote your heater’s efficiency.

If your furnace operates primarily on oil, it can also produce a diesel smell if the unit fails to ignite all the oil that passes through the burner. Finally, an oil smell can be the result of internal spillage or leaks. Reach out to a trained technician to correct the issue before spills or fumes create other mechanical issues.

Plastic or Rubber Smell

Plastic smells can indicate that components within your furnace have malfunctioned and begun to burn. If left uncorrected, these components can overheat or melt and start a fire. An HVAC technician can help identify the source of the odor. For example, scorched wiring or a failing blower motor can both produce the smell of melting plastic.

Home services companies that also specialize in electrical work can correct issues like short fuses and replace damaged parts to eliminate these safety hazards. Alternatively, burning plastic can indicate that a foreign object, such as a toy or utensil, has fallen into the furnace. An inspector can remove this object before it results in a breakdown of your system.

Chlorine Smell

The presence of chlorine smells can indicate electrical or metallic issues. If you have ever been outside after a thunderstorm, you may have encountered a similar smell that occurs when the high temperature of a lightning bolt breaks nitrogen molecules and releases nitrates into the atmosphere.

Within a furnace, aging can cause worn components to seize up or stall. As a result, the furnace cycle may attempt to draw up additional electricity to push through the resistance. The additional voltage can create excessive heat within the motor. If this heat builds up enough to melt away wire insulation, the unit can begin to produce electrical sparks that create this chlorine smell. Home services companies with expertise in electrical work can solve these issues before they create household fires.

Dirty Locker Room Smell

If you get a whiff of old socks or the sour sweat odor typically associated with locker rooms, the cause is probably bacteria. Within a furnace, bacteria growth can occur on internal coils. These coils cool off during the fall and then rapidly reheat when you turn up the thermostat. This reheating process causes condensation, and the dark moist environment is the perfect setting for bacterial growth. Professional cleaning and follow-up maintenance can scourge this unpleasant growth and eliminate any foul smells.

Sewage Smell

The unpleasant smell of sewage can directly result from a dry sewer trap or sewer leak. In the household, sewer traps help prevent gas from escaping back into indoor air. If this trap dries out, the structure cannot perform its job correctly. Once you turn the heating back on for the winter, the warm air can blast gusts of these unpleasant gases throughout the home and cause a sewage stench.

Similarly, the purpose of a sewer line is to transport wastewater away from the home. If this line has a leak, the wastewater can pool beneath the house or indoors and cause bad odors. Home services companies that also specialize in plumbing can help diagnose and fix sewage problems.

Gunpowder Smell

A gunpowder or firework scent can indicate a fried circuit board within your heating system. Overblown motors can also release this acrid gunpowder scent. If left unattended, this internal damage can cause a safety hazard within the home. Reach out to a technician who specializes in electrical safety to correct circuiting problems within your heating system.

Negative Consequences of a Poorly Maintained Furnace

Overall, strange furnace smells can indicate that your unit needs maintenance and upkeep. Failure to properly maintain the furnace can result in serious problems, such as damaged heat exchangers or home fires.

Cracked Heat Exchangers

The heat exchanger is a thin metal component between the furnace’s combustion chamber and the blower. This device transmits heat from one area of the furnace to the other so that warm air can enter the rooms in your home. It is also responsible for helping to properly exhaust the carbon monoxide produced during the combustion process, so it leaves your home instead of remaining indoors. Over time, normal wear and tear can cause the heat exchanger to crack. An HVAC professional can identify evidence of damage to this device and replace it if necessary.

Home Fires

Any defects within a furnace can make the home more susceptible to indoor fires. These defects include gas leaks, broken furnace hardware, torn electrical parts, or dust buildup. For example, frayed electrical wiring can produce sparks that easily ignite into fires. Broken hardware can rattle within the unit and cause other parts to overheat. For the safety of everyone involved, it is important to schedule regular maintenance so the furnace functions correctly throughout fall and winter.

Contact Us Today

Strange furnace smells can compromise air quality. However, there is no reason to allow bad odors to disrupt your quality of life. AJ Danboise Plumbing, Heating, Cooling & Electrical offers heating system inspection, maintenance, and repair for Farmington Hills and surrounding areas. We can help improve the efficiency of your furnace to keep your home warm and safe throughout the season, turn to us for indoor air quality! Our company also specializes in electrical work, so there is never a need to worry about your panels or wiring. Contact AJ Danboise Plumbing, Heating, Cooling & Electrical today for all your home furnace needs.

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