Why Your House Smells Bad When You Turn On The Heat


There’s no reason to use your furnace during the summer, and even during the winter we only really notice the furnace when it isn’t operating the way it should be.  Even then, when strange and unwelcome smells come with the much-wanted heat, then we start to get worried.  While the foul odor is a bother if we’re expecting company, it could also be a sign of some further danger. Here are a few reasons why your house smells bad after turning on the heat:

Acrid Burning Odor

We all know the scent (well, at least those who don’t get a regular cleaning of their furnace before starting it up in the fall).  You turn on your heater when the temperature finally drops below tolerable and curl your nose at the pungent aroma of something burning.  Back in college, I did this once and set off the smoke alarm. So what causes this nasty smell that happens once and then stays clear for the rest of the season?  In a word:  Dust.  While not directly harmful, it’s unpleasant and can be easily avoided with a simple cleaning before you start up the furnace for the first time.

Musty Odor

Does the air smell, stale, musty, or somewhat dirty?  This usually goes hand-in-hand with flaring allergies and irritable noses. A dirty filter or dusty ventilation ducts are typically to blame for this.  The air smells dusty because it is.  Try replacing your filter or having your ducts cleaned. The filter itself needs to be replaced every 3-6 months depending on how heavily you use your central air.  You can also remove your vent and shine a simple light into the vent to see how dirty the air is.  We can help you with a full cleaning and re-sealing of your ductwork to keep your air smelling fresh.

Electrical Smell or Ozone

What about burning plastic, smoke, or the scent of ozone?  These are far more serious smells.  They could be caused by an overworked motor heating up (have you noticed reduced airflow from your vents?) or an electrical failure in or near the furnace.  This smell requires an immediate response.  Turn off your furnace, take a look at the furnace itself to make sure nothing is burning or smoldering, and call for an emergency repair immediately.  You’ll want your furnace back online soon, but a house fire is too warm for anyone. At Service Legends, we’ll be glad to head out as soon as possible to get your heat back online.

Rotten Eggs

This is more common for homes using a propane-fueled heating system (or have propane lines into the house for cooking or heating water).  Propane and natural gas have no odor detectable to human senses.  They are odorless and colorless, making them invisible to human perception.  Since this gas is dangerous to humans, the powerful, and very evident, the scent of rotten eggs is added to it.  If you pick up a whiff of this odor whenever your heater is running, turn off the furnace and call a professional to find the source of the leak.

These are the most common smells you’ll encounter from your central heating.  Others require more drastic cleaning measures as you’ll occasionally smell the scent of sewage from an open black water line or even decay from animals that have snuck into your ventilation system over the summer.  This is all why Service Legends recommends a full service each fall before you turn on your system for the first time!

Heating and Cooling Des Moines Since 1997

At Service Legends, we take pride in heating and cooling Des Moines and the surrounding areas. Our HVAC services include furnace and air conditioner installation, repairs, maintenance, and tune-ups. Our lineup of Indoor Air Quality solutions includes whole-home humidifiers, air purifiers, and air filtration systems. We can even help with HVAC financing.

Call 515-657-6634 to contact our Home Comfort Heroes today. We’re standing by 24/7.

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