Stinking Furnace? Here Are 5 Possible Causes

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woman covering her nose

If there’s one part of your home working harder than anything else throughout this winter season, it’s your heating system.  With the cold outside, your furnace is likely on overtime trying to keep you and your family members warm during these chilly months.

As such, it’s important to keep your furnace in tip-top condition so it can serve its purpose properly. When your furnace—and your home’s HVAC system as a whole—is well-maintained, it keeps running without issues.

HVAC specialists RayMoore Heating & Cooling also said that heating systems must be professionally inspected not only to ensure peak performance but also to maintain manufacturer warranty coverage.

But sometimes, cleaning and maintenance fall to the wayside and your furnace lets you know it by emitting unpleasant odors. If your furnace starts to stink, don’t ignore it.

Below, we list down and describe strange furnace smells and what they might mean for your heating system.

1. Rotten Egg Smell

If you have a gas furnace and there is a sulfuric or rotten egg smell in your home, it’s a sign of a gas leak. Most gas furnaces use natural gas, which has no odor. To make gas leaks easier to detect, gas companies add mercaptan, a sulfur-based chemical that emits the rotten egg smell.

Inhaling gas is a huge health hazard, so get out of the house and call your HVAC service provider the minute you smell the mercaptan.

2. Burning Smell

During summer and spring, your furnace simply helps blow cool air throughout your home’s HVAC system instead of producing and circulating warm air. Essentially, your furnace remains unused for months after winter.

As a result, dust and debris gather within the ducts. And when you use the furnace come colder seasons again, the piles of dust that accumulated get burnt first, thus producing a burning smell.

This isn’t a cause for concern unless the smell persists for over 24 hours, which may point to a more serious problem. This is also why it’s important to get your furnace ready for the winter after months of neglect.

3. Burning Plastic or Rubber Smell

When plastic or rubber is heated, they produce a distinct foul smell. When you smell this, it’s likely that a plastic or rubber component of your furnace is heat damaged.

On instances like this, call your HVAC technician immediately, so they can check for any signs of burning and prevent further damage to your furnace.

woman covering her nose due to bad smells

4. Electrical Burning Smell

If you’ve ever smelled electrical wires short-circuiting before, you’d know they produce a sharp burning scent, similar to that of chlorine or ozone. When your furnace overheats, it produces a similar odor.

Furnaces overheat for a variety of reasons, from insufficient airflow and dirty components to the unit’s short cycling and old age. Whatever the reason may be, it’s important to contact your HVAC technician right away and have your furnace checked. Otherwise, your furnace becomes a fire hazard.

5. Musty Smell from Vents

If your vents blow not just warm but musty-smelling air, too, the problem might be in your vents. Mold and mildew can grow in the air ducts throughout your furnace system thanks to moisture buildup.

While the musty smell might be a mild annoyance, ingesting mold spores can pose a serious health problem.

This case is another great example of why HVAC maintenance is a must. With your ducts regularly serviced, mold and mildew will have less time to grow.

But in case there’s already mold growth in your ducts, don’t wait too long to call your HVAC maintenance provider and your furnace system cleaned or your ductwork replaced.

Your furnace ensures you and your family remain warm and comfortable all year round. Keep it running without trouble for years with proper furnace maintenance.


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