What To Do If Your HVAC Exhaust Smells Like Gas

Posted on Sep 15, 2020

Your HVAC system is probably one of your most used appliances, especially here in Hawaii. Even if you do not notice it running (which is a good sign!), your heating and cooling system is working to keep your home comfortable and healthy. So when you notice an issue with your HVAC system, it can be a little alarming. One main thing homeowners may notice is when their HVAC system smells like gas (sometimes when running the furnace, others while running the AC). In some scenarios, the smell of gas or other strange scents are easy to fix, but other times, these strange smells from your HVAC system can be the symptom of a serious problem.

First and foremost – if there is a strong smell of gas throughout your home, or if you hear hissing, turn off your furnace and get everyone out of your home. Immediately contact your local gas company or emergency responders. This could be the sign of a gas leak.

While that is a pretty scary introduction, gas leaks can be a serious hazard in your home and should not be taken lightly. However, if you are smelling gas in a certain area or only during certain times, there may be another explanation. Let us take a look at some of the most common scenarios and why it may cause your HVAC exhaust to smell like gas. 

HVAC Smells Dusty

The issue: If you have not started your HVAC system for a while, like in a vacation home, you may smell a strange scent when the heat first kicks on. It might smell like rotten eggs or a gas burning smell. During the summer, dust may settle within the HVAC unit or system, and when the furnace turns on, the dust gets burned off.

The solution: If the scent is coming from your furnace when you first start it up for the season, it is likely dust burning off. The scent will go away on its own over a short period of time. It should also be said that cleaning your ducts should be a regular thing, it’s a popular HVAC myth that you should only have a cleaning when you see dirt in the ducts.

Furnace Exhaust Can Smell Like Gas

The issue: The gas from your furnace exhaust pipe (which expels outdoors) is blowing back through an open window or door to your home. It is totally normal to smell a gas smell in the exhaust from your HVAC system, as this is how it expels used fuel or gas that may not have been completely used in your system. This is typical and how your HVAC system should function.

The solution: Pay attention to when you can smell this scent. Maybe you just need to close a window or door when the wind is blowing a certain direction. 

Trash or Compost Smells Like Gas

The issue: It may not be your HVAC system at all! Is your trash or compost pile too close to a window or living space in your home? You might not be smelling gas at all. That rotten egg smell may just be last week’s breakfast! (This might also be true for a propane grill that is close to the house!)

The solution: Take out the trash, or move your compost pile to a less intrusive location. 


The issue: Alright, here is the serious one! If you smell gas coming from your air vents, if the smell is constantly there or throughout the home, and if you hear a hissing or whistling sound near your gas appliances, this could be a gas leak.

The solution: This is serious. Evacuate your home immediately, taking all family and pets with you. Call your local gas company or emergency services, and tell them you suspect a gas leak. Do not create a spark of any kind (including an electrical charge, match or lighter). 

Preventing A Gas Leak

There can often be circumstances beyond your control when it comes to gas leaks. However, there are some things you can do to prevent a leak or help alert you if something is wrong.

  • Buy a carbon monoxide detector – Carbon monoxide is odorless, and produced when fuel is burned (like when your furnace runs.) It is also deadly, so you’ll want a detector to alert you when there may be a leak in your home.
  • Maintain your HVAC system – In previous blogs, we have discussed the importance of routine maintenance for your furnace and HVAC system, but we really can’t stress this enough! Because you usually only notice your HVAC system when something has gone wrong, annual maintenance will ensure a professional is inspecting your system for potential issues, and able to perform preventative maintenance so your HVAC system will be operating successfully for years to come.

Starting Preventative Maintenance

Has it been a while since you had your HVAC system maintained? Now is the time to schedule your annual maintenance, before you have an issue with your heating or cooling systems. Contact the team at AirPro Indoor Air Solutions to schedule your annual maintenance today.

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(808) 832-1178