What to Do When Your Furnace Smells Like Gas When Off?

Learn what could lead to this smell from your furnace and how to fix this issue

What to Do When Your Furnace Smells Like Gas When Off

Since a furnace is a heating appliance, it is normal for it to get warm while running and, thus, emit a light smell of warmed steel, for example. However, people often notice that they start sensing a smell of gas near their unit, which makes homeowners scared!

What to do if your furnace smells like gas when it’s turned off? How dangerous can it be? Why does it happen?

We will try to answer these questions today. Read on to learn what can make your furnace smell like gas and what steps should be taken to fix it. Also, we will explain a few other familiar smells that may come from this heating appliance.

With the help of this information, you will be able to figure out how serious the “smelly” problem is and whether your furnace requires any serious repair.

What Shall I Do If My Furnace Smells Like Gas When Turned Off?

This is not normal if you can sense the gas smell from the furnace. A properly operating unit that is not broken should not emit such odors. However, it’s often a stumbling stone for people to figure out what to do in this case.

Why Does My Furnace Smell Like Gas When I Turn it ON? - Comfort Master Heating & Air ConditioningWhy Does My Furnace Smell Like Gas When I Turn it ON? – Comfort Master Heating & Air Conditioning

First of all, you need to calm down. Yes, the gas smell around your furnace is not a good sign. It likely means there is a gas leak. But it could also mean you have a dead mouse or another rodent in the attic somewhere! In fact, you may sense a “gas smell” from anything that has the odor of rotten eggs.

So before you call for HVAC service, we recommend you look around and ensure you don’t have a dead rodent in the attic. Finally, ensure that nothing around your furnace has a rotten smell and could be a problem.

Finally, if there are no dead rodents, call your gas company to arrive and check your furnace for you. It will allow you to be 100% safe and ensure everything is fine. At this point, note that some gas companies will offer this service free of charge. However, quite many of these companies will charge you for a service call even if there is nothing to repair, and they will just take a look at your unit!

Sometimes, you can also call the non-emergency number for the fire department (as an option), and they may send someone to check the furnace for you.

But you should always pay attention to this issue! If there is a problem with your heating appliance, it must be addressed as soon as possible!

What Shall I Do If My Furnace Smells Like Gas When Turned Off
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Properties of Natural Gas and Propane and the Danger | Gas Leaks

When you sense a gas smell from the heater, it most likely means a gas leak somewhere. And as all of you definitely know, gas leaks are nasty things to cope with!

First of all, it is essential to remember the properties of the specific combustible gas your system uses. It will help you to decide how to act to cope with the problem.

Do you have a large tank outside?

In this case, the gas you have is propane. If you also have a meter with associated piping outside, then you likely have natural gas. It is crucially important to remember that the properties of these gases are different!

Besides, each of these gases will affect you differently. Here’s how it can do this:

  • Propane is heavier than air and will settle in low places (lower parts of the room, basement, etc.).
  • Natural gas is lighter than air. It will settle in higher places and dissipate through natural venting, especially in an attic.

Since any gas is explosive, the second you sense a gas smell, ensure you don’t smoke! Also, don’t turn on electrical devices, including lighting! You better use a flashlight instead until the problem is fixed.

If the odor is heavy, you must immediately leave your home and call your fire department! Make sure to evacuate other people and pets inside the building. Additionally, if you have natural gas, you could also turn off the gas service at the meter. You need to turn the gas off at the tank for propane service.

Now you know what to do if you sense a gas smell around your heating appliance like a furnace. In addition, we explained how gas may affect you and what should be done to prevent it from spreading around your home in case of a gas leak.

What Can Be the Cause For Gas Smell Coming From Furnace?

For many reasons, you can sense a gas smell when the furnace is off. One of them is a gas leak, which is also the most threatening cause. However, several less dangerous ones should still be addressed as soon as possible. Most of them can be spotted when the appliance is running.

Why Are Odors Coming from My Furnace? | GAC ServicesWhy Are Odors Coming from My Furnace? | GAC Services

Burning Dust May Cause a Gas Smell

This is one of the most common reasons your furnace smells like gas when running. But luckily, this isn’t a serious one. Generally, this problem will occur if your furnace doesn’t work for an extended period (for instance, if you have not been using the house for a while).

If your furnace has been off long enough, a strange smell like burning gas or rotten eggs may appear when you start the HVAC system again. It happens because accumulated dust is being burned off. 

If the dust is indeed the case of your problem, there is no need to worry. The smell will disappear itself after a short while. The best thing you can do to get rid of it and prevent its occurrence is to clean the system that has not been in use for a while. Regular cleaning of the ducts is also recommended.

Burning Dust May Cause a Gas Smell
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Start of Each Cycle May Lead to a Furnace Smelling Gas

Sometimes people report that they notice a faint gas smell, which disappears pretty fast. This is often a result of the furnace’s kick-on, kick-off cycle. Typically, a furnace will kick on and off around three to eight times every hour. At the end of every cycle and the start of another, there might be a faint gas odor coming from your heating appliance.

In most cases, this isn’t a cause for alarm, but you should not ignore it anyway! The best thing to do would be to call a technician to inspect the system and diagnose any problems.

Check Your Furnace For an Exhaust Pipe

There might be a gas smell coming from your furnace because of the exhaust pipe. This pipe is supposed to transfer the burnt gas safely to the outside, but it may go wrong. If there is a gas smell in your house, the gas is getting back into the building somehow.

Start with trying to pinpoint where the gas is coming from. If the gas is coming through the window or door, it’s most likely getting in with the wind blowing it from the exhaust pipe.

So if the cause of your furnace gas smell if the exhaust pipe indeed, this is normal and there is no need for panic. The thing is that the exhaust pipe might carry some unburned gas, causing an unpleasant smell indoors. However, we still recommend you call a professional HVAC technician to inspect the furnace and the pipes.

Check Your Furnace For an Exhaust Pipe
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Trash or Compost Might Be the Cause Of the Odor

On rare occasions, the source of the problem might not even be in your furnace! Sometimes, you may sense a gas smell coming from that trash pile left unattended in your backyard.

Check around your house to see if it’s there. If you have some trash or compost near your windows, it might cause a gas-like smell. If the trash/compost pile has been there for a while, it has already decomposed. As a result, the smell might resemble that of rotten eggs.

It Could Be a Gas Leak!

This is the worst scenario that can happen! If the gas smell is caused by gas leakage, you should take it seriously and act quickly. A gas leak can have grave consequences if not managed as fast as possible. For instance, it can lead to carbon monoxide poisoning or even a gas explosion!

To detect a gas leak, look for the following signs:

  • Your house constantly smells of gas
  • You can hear hissing or whistling noise near your furnace
  • There is a gas smell coming from your air vents

If you notice any of these signs, turn off the system and evacuate your household dwellers immediately. When you are at a safe distance, call your local gas company to come and inspect your HVAC system.

Now you know more about the possible reasons for a gas odor in your house or apartment. Although not all of them are potentially dangerous, you should still be careful and pay attention to the most minor signs of weird odors coming from your furnace and other heating appliances! It will help you detect the problem on time and safely fix it.

It Could Be a Gas Leak!
Elnur_ via VistaCreate

What Odors May Come From My Furnace?

Sometimes, your furnace may smell strange. But mostly, people find it hard to define the odor’s origin. So here are a few most common smells you can sense from your heating appliance, as well as their possible sources.

  • If your furnace smells like burning, it’s probably occurring when you turn on your furnace for the first time.
  • If your furnace smells like burning plastic or burning rubber, it might have an electrical problem.
  • A burning smell can also come from your furnace’s motor, which is too hot, or when the heat exchanger is cracked.
  • If your furnace smells like a sewer or rotten eggs, there could be a problem with your sewer lines.
  • If your furnace emits musty odors, mold and mildew are probably inside of it.
What Odors May Come From My Furnace
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What to Do to Prevent Gas Smell From Your Furnace?

Since a gas leak is a serious problem, measures should be taken to detect it as fast as possible and prevent it. Here are the most effective preventive measures:

  • Regular furnace maintenance. It will ensure that every part of the system is running well.
  • Carbon monoxide detector to detect the presence of carbon monoxide in the household.

Remember that the burning fuel in the furnace produces carbon monoxide. As the gas is odorless, it can be pretty hard to notice it, but a detector will allow you to do that at once!

Now you way more about smelly furnaces! We told you what may cause your heating appliance to produce various odors and what to do should this happen to you. Also, you have learned a few smells that may come from a furnace and their possible causes.

Finally, we explained what steps to take to quickly fix your smelly appliance (if there is no serious issue like a gas leak, of course!). And please remember that if there is the tiniest chance for a gas leak, you must not try to fix it yourself!

Evacuate your family safe and stay away from your house. Also, call for gas service to arrive and address the problem.

What to Do to Prevent Gas Smell From Your Furnace
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Frequently Asked Questions

⭐Should I smell gas from my furnace?

No, you should not smell gas from your heating appliance. If this happens, call for a specialist to come and check it for you!

⭐Why does my AC smell like gas?

It can be an indication of a fuel leak. As with exhaust fumes, the inhalation of gas fumes can be hazardous.

⭐Is it possible to fix a gas leak myself?

No way! This must only be done by a gas service professional!

Written by
Camilla is an experienced Consultant with more than 20 years of preparing professional articles for numerous online resources. She has done a tremendous job and has learned a lot during her career. Camilla will advise you on the latest trends and give amazing tips on how to decorate a house.
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