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This week here on Tech Tips we’re going to talk about one of if not the most common question we hear about furnaces. “Why does it smell burnt when I turn on my furnace?” and it’s a relatively simple answer, but it could also be a sign of a larger problem as well. So we’re going to break it down for you here.

Over the course of the year, our homes collect a lot of dust and dirt. This is pretty common and we all have it, but during the warmer months you’re not using your furnace. This means that any dust or dirt that has made it into your HVAC system over that period of time has collected on the heating components of your furnace.

So when you use your heat for the first time that dust and dirt is usually burned off of the surface of the components and in most cases is harmless and normal. If you’re noticing that the smell doesn’t go away after a few minutes, it could be a sign of a problem with your heating components. At this point it’s probably a good idea to contact an HVAC professional to inspect your furnace and make sure it’s safe to use and all of the components are working properly.

As with anything mechanical over time, part wear with usage and your furnace sits unused for a portion of the year which could lead to the failure of a part or component. This is why it’s important to make sure you’re having regular maintenance visits like with our Superior Club membership. This allows a licensed HVAC technician to regularly see your equipment and catch mechanical failures before they happen. Which could save you thousands and extend the life of your furnace and HVAC system as a whole.

If you’d like more information about our Superior Club membership or just want to schedule a furnace check up, give Superior Heating Cooling Plumbing a call 314-209-7500

Check back next week for a new Tech Tip!

Furnace Smells like Burning Plastic

The smell of burning plastic is a distinct scent and a sign that something is melting in your furnace. Oftentimes, a water bottle cap, toy, or other plastic object has found its way into the furnace and is now succumbing to the heat.

This smell can also be the result of frayed wire shielding melting. Over time, the plastic shielding can become worn and cracked and fall into the furnace, causing that plastic smell. You will want to shut down the furnace and clean the plastic out in order to get rid of the smell and make any necessary repairs.

Gas Smells

You may notice a faint smell of gas when you are standing near your furnace. This is common and nothing to worry about. However, a stronger smell of gas throughout the entire home is a sign that you have a large and dangerous leak on your hands. You should immediately turn off the furnace and call a trusted HVAC expert to pinpoint and repair the leak.

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Rotten Eggs

Natural gas doesn’t actually have an odor, which can make it difficult to detect. That is why gas companies will often add a chemical known as mercaptan, which is responsible for the sulfur or rotten egg smell. Mercaptan acts as a safety precaution that is meant to alert homeowners when there is a natural gas leak. Remember that natural gas is highly flammable and combustible, so you will want to take action immediately.

Dirty Socks

If your furnace smells like a locker room full of dirty, sweaty socks, you could have a problem with bacteria build-up on your heating coils. Throughout the changing seasons, the heating system coils repeatedly cool down and heat up, which can lead to condensation and where there is moisture, there is probably bacteria. The good news is that you can fix the problem with some elbow grease. You will want to start by changing your furnace filter and cleaning the evaporator coils. It might also be a good idea to invest in professional air duct cleaning services to completely eliminate the problem.


During the warmer months, when your furnace isn’t in use, it is natural for dust and dirt to collect. As a result, you may notice a dusty smell the first few times you fire up the furnace. This is nothing to worry about and the smell will eventually go away as the furnace burns up any residual dirt. If the smell persists, be sure to replace your filter.


Furnaces tend to be housed in basements and other damp parts of the house. Over time, this moisture may cling to the furnace. When the furnace is turned back on, it may take some time for the moisture to burn off. The smell will eventually pass and isn’t a sign of something serious that you need to worry about.

Metallic Smell

A metallic smell is an indication that a component in your furnace is overheating. Most likely, it is the blower motor, which can wear out over time and cause the furnace to use excess voltage, which will cause it to overheat. This problem can then lead to melting wires and more burning smells. Your best bet is to shut off the furnace and call a professional. Continuing to run the furnace could cause major damage and result in expensive repair bills.

Oftentimes, your nose is your best line of defense when it comes to making sure your furnace is in working order. While certain smells are normal, especially when you are turning the furnace on for the first time that season, others can be an indication of a serious problem. Don’t make the mistake of ignoring these smells and schedule furnace repair as soon as possible.

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