Best Summer Ever Sale Event

Learn More

Different HVAC Smells and What They Mean

We’ve all been there. You haven’t been using your air conditioner during the cooler months of the year, and when you finally turn it back on to cool down the house again, you’re met by some very strange smells.

It’s important to know what the different odors mean and how to take the proper measures to remedy any issues that are causing these HVAC smells.

Rotten Eggs

A rotten egg smell from your HVAC system could be a natural gas leak. Natural gas is odorless, but the sulfur in it gives off a foul smell when it mixes with the air. If you smell natural gas, turn off all ignition sources and leave the house immediately.

If you need help determining whether or not you have a natural gas leak, contact your utility company. If they confirm that there’s no leak, you can call us to inspect your HVAC system.


Sewage smells are caused by the foul gasses from fractured sewer lines. These odors can come from your HVAC system when installed has been installed near a sewer line. The smell may have lingered into the supply ductwork.


The smell can sometimes be powerful, depending on how close you are to the sewer lines and how much sewage has backed up into them. This is why you may smell sewage coming from your AC unit: Your system is close enough to have these gasses waft into your home through your vents.


If this happens, get in touch with the professionals needed to find and eliminate the problem. Plumbers and HVAC technicians are the best people to call.

Dirty Socks

A dirty sock smell coming through the HVAC vents is a telltale sign that you need to clean your air conditioner’s evaporator coil. This part of your HVAC system cools and dehumidifies the air before it enters your home.

Mold and mildew grow in areas where moisture accumulates, such as inside your home’s ductwork and HVAC systems. The dirty sock smell that results from this growth is usually most noticeable when you turn on your air conditioning because it forces air through this area of the system.

Mold can cause health problems, especially if it grows inside ductwork where people breathe in the released spores. It’s best to leave this type of job up to professional HVAC contractors who have experience cleaning out mold from inside units and ductwork.


The smell of musty air is usually a sign of a problem with your HVAC system. It can come from several different places in the system, so it’s important to find the source of the smell and fix it.

Mold and mildew tend to grow in damp environments. If your HVAC system is not working right, there may be leaks or water damage. This can lead to mold growth to inside your ducts and other parts of the system. You may notice this smell when you turn on your air conditioner or heater or if you walk into a room that has been closed up for long periods of time.

The best way to fix this problem is to call a professional HVAC technician and have them come out to check your system and clean it out if necessary.

Electrical Odors

If you can smell an electrical odor when you turn on your AC unit, the problem may be in your air filter or blower motor. Your air filter should be changed every three months during the summer and once a year during the winter. If your filter is dirty, it will restrict airflow and cause your system to work harder to cool your home.

hvac filter replacing. Replacing the filter in the central ventilation system, furnace. Replacing Dirty Air filter for home central air conditioning system. Change filter in rotary heat exchanger recuperator.
If you have checked and cleaned your filters and are still having problems with electrical odors from your HVAC system, it could be as simple as replacing a capacitor or relay in the circuit board of your condenser unit or evaporator coil.

If you smell electrical odors coming from your HVAC blower motor and/or ductwork, it is important to have them checked out by a professional as soon as possible. An electrical fire could start if the problem is not addressed quickly.


The smell of oil in your home isn’t uncommon, especially if you have an older heating and cooling system. The oils inside your system lubricate parts like compressors and motors and provide insulation for electrical wires.

video here
If these oils leak out of your system, they can cause damage to other parts that come into contact with them. They can also cause a fire hazard if they drip onto hot coils or burners within the furnace or air conditioner unit itself. Call us as soon as possible.

Struggling to find the source of your HVAC smells? Contact the HVAC experts at Adeedo to get rid of those annoying odors.

Skip to content