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4 Signs Your Furnace Is Trying To Kill You

November 9, 2021 | Blog

This isn’t the title of a new horror movie. Furnaces can be dangerous if you ignore crucial warning signs. From fire to carbon monoxide emissions, your furnace could cause serious harm to you or your home.

Furnaces are like every other appliance, and repairs can easily be made when needed. At Air Clinic San Antonio, we offer expert heater maintenance and repair for the San Antonio area. 

Loud Sounds

Furnaces shouldn’t be making any noise, let alone strange ones. In fact, modern furnaces are designed for noise reduction. The most you should hear from a furnace is a faint rumble when it starts up. 

Any unusual sounds may indicate a problem. Here are some sounds a furnace can make and what they may mean.


If you hear rattling, it may be from worn down or broken parts in the motor or fan. If ignored, this may lead to a sudden breakdown.


Clicking is a typical sign of a problem with the ignition. It could be a faulty flame sensor or an issue between the gas and the ignition. If you hear persistent clicking, contact a technician immediately.


Like a vehicle, a squealing sound could point to a faulty belt or fan motor. These are simple fixes, but can’t be done on your own. Contact your local HVAC company for routine repairs. 


This sound is more common in older furnace models. Booming indicates a buildup of gas from an ignition delay. A furnace with too much gas pressure could severely damage internal parts and might even start a fire. If you hear frequent booming noises, get it checked out right away. 


During the beginning of furnace season, this sound isn’t anything to worry about right away. It’s usually the unit slowly coming back to life after the warm months. If this noise persists, it might be a sign of damaged fan belts. This requires repair and routine maintenance. 

Unusual Smells

Like strange sounds, unusual furnace smells aren’t something you should ignore. Not only are they unpleasant, but they could be signs of a serious problem. Here are three scents that might indicate a system breakdown or a serious danger.

Dusty Or Burning

If you smell these at the beginning of furnace season, it’s nothing to worry about. It’s just the furnace slowly starting to work again, and the smell might be because of some unseen dust. It will stop once all the dust is burned or blown away. 

If this smell doesn’t go away after a while, it might mean there’s a buildup of dust. Blocked air filters are serious risks for furnace fires. If the smell still continues after changing the filter, you should contact a professional for help. 

Rotten Egg

If you smell an odor like rotten eggs or sulfur, evacuate your home immediately. This smell is an almost guaranteed sign of a natural gas leak. Fuel providers include the odor-causing chemical mercaptan in scentless gas to alert homeowners of a leak. 

If ignored, gas leaks can lead to:

  • Carbon monoxide poisoning
  • Fires
  • Explosions

Evacuate your home and call the local fire department and utility company for help. Even if you suspect the smell to be something else, it’s best to take all precautions. 


Metallic smells could indicate the internal and electrical components are overheating. It could smell like hot plastic, metal or rubber. If you suspect the inside of your furnace is getting too hot, immediately turn off and unplug it. Then, call an HVAC technician for an inspection or repairs.

Monitor the furnace in the meantime. Overheated furnaces can lead to irreparable damage and even fires. 

Change In Burner Flame Color

Burner flames in a gas furnace should always be blue. This color means safe and efficient combustion. No gas is being wasted, and everything is working as it should. 

If the flames burn yellow or orange, this is a sign of a combustion problem. Because the gas isn’t burning properly, it could lead to the presence of carbon monoxide. CO is a dangerous, potentially lethal gas. 

If your burner flame is any color but blue or almost entirely blue, it shouldn’t be ignored. Turn off your furnace right away and contact a professional for cleaning and repairs. 

Rusted Flue Pipe

Located at the top or rear of the furnace, the flue pipe vents gas out of your home. If you notice this pipe has become rusted, it might be a sign of improperly vented carbon monoxide. 

The flue system vents all gas byproducts from the furnace. If something is damaged in this system, it could corrode the flue pipe and send CO into your home. You should schedule an inspection the moment you see this pipe begin to rust. 

Call A Technician

When you notice any of these signs, the best thing to do is call a professional to inspect or repair the problem. If you’re in the San Antonio area, Air Clinic San Antonio is your go-to HVAC company. 

Our team of skilled technicians can detect and fix any problem your furnace may encounter. We promise expert services with a 100% satisfaction guarantee! Contact us today for all your repair needs!

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Proud to offer the best products from top HVAC brands including Trane, American Standard and Carrier.

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