Is It Normal to Smell Gas Near a Furnace?


Natural gas furnaces provide amazing heating capability and convenience. There is no need to truck in fuel, and it produces very little soot, making it a very easy furnace to maintain.

With all that is good with these furnaces, should you be concerned if you smell gas near your unit? Keep reading to learn what you need to know if you smell gas near your furnace.

Important: Read This First

If you have a strong smell of gas or hear a hissing hear your furnace, you may have a dangerous gas leak. Turn off your furnace, and immediately evacuate your house. Do not operate any lights or switches in the house on your way, as these can cause a spark and ignite the gas.

Once everyone is outside, call 9-1-1 or call your natural gas company. They will tell you what to do from there or will dispatch someone with more experience to investigate and help.

While not every case of a gas smell is cause for concern, you should take every case seriously. Natural gas is extremely dangerous when improperly controlled. Do not be lulled to ignoring a smell, and suffering possibly catastrophic consequences.

Why Is a Gas Leak Dangerous?

Everyone knows a gas leak can be dangerous, and most people immediately think of the fire hazard. Given the connection between buildings, this danger extends beyond a single home or building. However, this is only one component of the hazards of natural gas when there is a regulation problem.

Another incredibly important danger is what it does to the composition of air. Humans need oxygen, and normal air contains about 20% oxygen by concentration. When natural gas leaks into a home or sealed building, it reduces the oxygen content in the air.

When the concentration gets down to about between 10%-12%, you may notice your lips turning blue or purple. If it gets down to 6%-8%, then you may lose consciousness and suffer asphyxiation. This reduced oxygen content causes a number of symptoms, including:

  • Headache
  • Dizziness
  • Nausea
  • Fatigue
  • Throat irritation

Besides displacing oxygen in the air, it can also release carbon monoxide into the air. This gas can be very dangerous, leading to similar symptoms as natural gas, and possibly leading to death.

Why Does Gas Smell Like Rotten Eggs?

Natural gas does not have a smell when it is extracted from the ground. However, given the dangerous nature of the gas, companies add a chemical called mercaptan. This is what gives the distinctive smell of rotten eggs.

Federal regulations require this additive to make it easy to detect. This chemical is not corrosive and is very distinct. When there is a significant leak, the chemical smell will be extremely strong, and may even burn your nostrils a little. Prolonged exposure can also cause similar symptoms to carbon monoxide and natural gas poisoning.

Why Would I Smell Gas?

If your furnace is operating properly, you should not have the smell of gas. If you do, it indicates one of many possible problems, that should be fixed immediately.

The first obvious problem is a gas leak in the supply line. If this is the case, you have a major problem and need emergency assistance. Fortunately, these kinds of leaks are rare without some other kind of accident to cause them.

One fairly common reason is the furnace exhaust being blown back in through an open window. The good news about this is that your exhaust system is working properly. If you notice the smell when it is windy outside, look to see if there’s a window or flue open downwind from your furnace exhaust pipe.

Sometimes a furnace will emit a faint gas odor when it first cycles on. Pay attention to see if it dissipates quickly after the furnace cycles on. If so, your furnace may need maintenance to ensure the draft system is working properly.

There are several other components that rarely malfunction, but could cause the smell of gas if they do. The best course of action is to call the professionals at Integrity Heating & Cooling to diagnose and repair the problem safely.

When Should I Call for Help?

Knowing when to call for help, and who to call is important to getting this smell of gas fixed quickly. Here are a few quick questions to determine how dangerous your situation may be. If you can answer yes to any of these questions, then you need to leave your home immediately and either call 9-1-1 or your gas utility company.

  • Is the smell constant, or does it seem to come and go?
  • Do you hear a whistling or hissing near your furnace?
  • Are your CO2 or carbon monoxide detectors going off?
  • Does the smell seem to be coming from your vents? Be sure to crack a window before checking this one.

Ways to Prevent a Gas Leak

The best way of dealing with a gas leak is to prevent them in the first place. Here are some easy ways to keep your gas systems working safely.

First, install and maintain a carbon monoxide detector. Carbon monoxide is produced when fuel is burned, and is just as dangerous, though is often undetectable without the aid of a detector. If this goes off, you know you have some leak in your furnace system. Get this fixed immediately.

Next, perform regular maintenance on your furnace. During these visits, a trained technician will inspect the unit to ensure all components are operating correctly. They will also check to ensure there are no gas leaks, even minor ones.

During your maintenance visit, your technician may find some components that need to be replaced. Making these repairs quickly will prevent major problems in the future.

Do I Have to Replace My Furnace?

You may think that if you have the smell of gas, you will have to replace your furnace. This is not always the case, depending on the exact cause.

Most forced-air gas furnaces will last 15-20 years when properly maintained. If you are smelling gas, and your furnace is nearing this age, you may be best served to replace your unit. A new unit will mean you are less likely to encounter recurrent problems in the near future.

However, not all leaks will require a replacement. If your furnace is newer, or the leak is coming from the supply line, then a basic repair may work. Your technician will diagnose the problem, and then help you evaluate your options. Generally, if your annual repairs equal 50% of the cost of replacement, you are better to replace the unit.

Integrity Heating & Cooling has been providing Charlotte with furnace installation, repair and maintenance for the last 35 years. Beyond heating services, our team also provides air conditioning installation, service and maintenance, along with ductwork and sealing and air quality improvement. Save our number on your phone, and then give us a call to troubleshoot your gas smell problem.

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