Why Does My Furnace Smell Bad When I Turn It On?

HVAC technician troubleshooting an air conditioning unit. Conejo Services logo on shirt.
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When it is too cold outside, there is nothing better than stepping into the comfort of your home, especially when the heater awaits you. But there is one thing that can spoil the moment: an unpleasant odor coming out of the furnace. Bad smells can indicate that something is “off” with your furnace. However, it is quite a common issue, and depending on what’s causing the smell, it can be easy to eliminate and, even better, prevent. 

The air we breathe impacts our health, and our home’s environment should be kept as healthy as possible. When there are foul odors circulating indoors, it lowers our home’s indoor air quality (IAQ). The furnace not only provides your home with comfort, but it can also improve IAQ thanks to its specialized filters. However, if the unwanted smells originate from your furnace, you need to quickly find the cause behind them for your comfort and your furnace’s health. The odor could smell like anything, such as exhaust fumes, dirty socks, gunpowder, or even chemicals.

Let’s go over some of the most common furnace smells and find the reasons for their occurrence.

Furnace Smells Like Gas or Rotten Eggs

If you smell rotten eggs or something that smells like gas, there’s probably nothing wrong with your furnace, but there’s a high chance you’re dealing with natural gas leaks in your house.

Natural gas has a sulfur-like additive to alert you when there’s a leak, so if you have a furnace smelling like rotten eggs, we advise you to:

  • Switch off your gas supply
  • Open the windows 
  • Promptly exit your home
  • Contact your gas company immediately

What about a smell that’s not quite rotten eggs, but it’s something horrible? If you notice a putrid smell when you turn on your furnace, you might be dealing with a dead pest. Mice, rats, and other critters can crawl into your air ducts and emit a foul odor when they die. If this is the case, contact pest control to remove dead animals, then schedule a duct cleaning service from the local HVAC experts to remove the smell permanently.

Furnace Smells Like Burning or Gunpowder

Does it smell like something is burning when you turn on your furnace? You may notice a burning smell the first time you turn on your furnace or if you haven’t used it in a while. This is perfectly normal, and the smell should disappear soon.

If your furnace still lets off a burning smell after having it on for more than thirty minutes, you could be facing a more severe problem. First, check your filter. If it is clogged, replace your air filter. If the filter isn’t clogged and you still have a furnace smelling like gunpowder, turn the furnace unit off and contact Conejo Valley Home Services for professional furnace repair services. Constant electrical issues, especially on an aging unit, are signs that it’s time for a new furnace. Do not attempt to fix this issue yourself! Call us immediately, as this can be a significant fire hazard.

Furnace Smells Musty

A musty smell usually indicates that there is moisture trapped inside your furnace. If the smell is faint or disappears after a few hours, this is no cause for concern. However, if the musty smell doesn’t seem to dissipate over the next few days, it may indicate that biological growth is growing inside your furnace. 

Since various types of biological growth can be toxic when inhaled, you should call a professional to come and assess the situation. Don’t waste precious time searching for “furnace repair near me” when you can call Conejo Valley Home Services at 805-499-0448!

Oily Smell

The smell of burning oil usually means that your furnace filter is clogged. You should replace your furnace filter every three months, though if your home has smoke, pet hair, and excessive dust, you should change it more frequently. Once you replace your filter, the smell should dissipate.

If changing the filter does not stop the smell, you should immediately contact a professional since this may indicate an oil leak inside your furnace.

Furnace Smells Like Dirty Socks

A dirty sock smell may indicate a buildup of bacteria in your furnace, and a buildup of condensation often causes it. The best way to rid your furnace of this unpleasant smell is to clean your furnace and replace your air filter. If the smell doesn’t disappear, the problem may be in your air ducts, which will need to be cleaned by a professional.

Chemical Smell in Furnace

Your furnace should not smell like chemicals. Chemical odors, especially if they smell like formaldehyde, may indicate that the heat exchanger in your furnace has a crack. 

A broken heat exchanger is a massive fire hazard and may also cause your furnace to leak carbon monoxide, which is deadly in huge quantities. Turn off your furnace and evacuate immediately before calling in a professional.

Let Us Help You Get Rid of Furnace Smells!

Your furnace is an essential appliance, and if you’re having problems with yours, you need to resolve them immediately. You don’t want to face a cold winter without your furnace, and the longer you wait to fix a minor issue, the bigger and more expensive the repairs will be. 

We’ve talked about getting rid of the causes, but prevention is an even better and more effective way to keep these smells away. Along with scheduling furnace repairs as soon as possible when you’re having a problem, you also want to consider signing up for a preventative maintenance plan to ensure your unit is always running at peak efficiency. You’ll save money on your heating bill this way, and repairs will be less frequent and cost far less when needed.

Are you smelling any of these obnoxious odors? You can rely on the HVAC specialists at Conejo Valley Home Services to diagnose the trouble quickly and affordably. Contact us today at (805) 499-0448!  We look forward to working with you!

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