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What To Do If Your HVAC Exhaust Smells Like Gas

Young Repairman Checking A Hvac Exhaust

HVAC units are some of the most reliable climate control appliances in your home or office. However, it might be time to check if you notice a gas or rotten egg smell coming from your air conditioner’s exhaust.

Weird or strange smells from an HVAC might indicate an unhealthy system or a severe problem. This is especially important if you notice any gas odors coming from the unit.

Gas odors from the exhaust system should never be taken lightly and can put your family and property at risk.

This article will examine what to do if the HVAC exhaust smells like gas.


Here are the simple steps to follow if your HVAC exhaust smells like rotten eggs or gas.

  • Do not use any electronics.
  • Evacuate the house.
  • Open windows and doors.
  • Contact the relevant people.
  • Keep everyone away.

Likewise, we will also look at why your HVAC exhaust smells like gas and how to prevent leaks in the unit.

Reasons Why You Might Be Smelling Gas From the HVAC Exhaust

White Vent Showing Dirt Grime
  1. Dust: One of the most common causes of your HVAC exhaust smelling like gas is due to dust. Dust that settles around the furnace can cause the smell as it is burned off. In most cases, the gas smell disappears or might even go unnoticed.
  2. Start of furnace cycle: Additionally, when the furnace in the system kicks off its cycle, you might notice a faint gas smell coming from the exhaust. In most cases, the HVAC furnace remains idle for a few minutes before starting a new cycle, during which you can smell the gas odor.
  3. Exhaust air getting back to the house: Another reason for the issue is if the exhaust fumes are blown back into the house. The HVAC’s exhaust pipe is responsible for safely expelling burnt and unburnt gasses from the unit to the outside. You might notice the gas odor if the air is blown back into the house.
  4. Gas leak: Gas leaks are the most serious cause of gas smells from your HVAC unit. They occur due to damage to pipes, gas tanks, or faulty parts in the system. Other signs of a gas leak include hissing near the furnace and a smell of gas from the system vent.
Fire Hazard

Natural gas or propane gas used by the furnace is highly flammable. Therefore, HVAC professionals should handle any gas smell or leaks.

Five Things To Do if Your HVAC Exhaust Smells Like Gas

As previously stated, any gas odors from your HVAC should not be left to chance. But, unfortunately, it can be too late before differentiating between a gas leak and exhaust fumes sneaking back into the house.

Due to the severity of potential gas leaks, it is crucial to follow the following steps in case your HVAC exhaust smells like gas.

1. Do Not Use Any Electronics

Smoking Smartphone Failure

Natural gas or propane gas is highly flammable, and sparks can ignite it. Therefore, all electronics should not be switched on or off if you notice a gas odor coming from the exhaust. In addition, do not make any calls when inside the house.

2. Evacuate the House

Family Emergency Leaving The House

Try to evacuate the house as soon as possible. Prolonged exposure to the gas can lead to some health complications or even passing out.

3. Open Windows and Doors

Opened Doors And Windows

Open up as many doors and windows as possible as you leave the house. Aerating the house will help let air flow through the rooms, reducing the gas’s concentration.

4. Contact the Relevant People

Fire Department

Once you get outside, make sure to call the fire department and gas company to come and help assess the issue. Likewise, follow all their instructions, like turning off the house’s main gas and power supply, if possible.

5. Keep Everyone Away

Family Outside The House

Lastly, keep all people away from the house except for the relevant personnel. After a thorough inspection by the fire department, they will give you the green light to return to your home.

Preventing Gas Leaks in the HVAC Unit

Regular maintenance is the ideal way to prevent gas leaks in your aircon. In addition, maintaining the system can help diagnose and identify potential damages or issues that can cause leaks in the future.


Early detection of issues in your HVAC system ensures that it runs efficiently and reduces the chances of gas leaks or damage to the unit.

However, just in case you start smelling gas or rotten eggs from the exhaust, the first precaution is getting out of the house to prevent any potential injury to you and the family.

Do not use any electrical devices until you are out of the house, and then you can call emergency personnel.

Frequently Asked Questions

What Causes My AC Exhaust To Smell Like Gas?

The most common reasons for your HVAC exhaust smelling like gas or rotten eggs are dust accumulation around the furnace, furnace cycling, exhaust fumes blowing back to the house, and a gas leak.

Can Fumes From the HVAC Furnace Be Harmful?

The fumes from the furnace have sulfur, carbon monoxide, and other gasses, which can harm your health. Contact a gas technician immediately if you suspect gas leaks in your home.

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