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Jun 15, 2023 2:36:38 PM by Logan Donahue

AC Odors: Causes, Solutions, and Prevention for Common Smells

Your air conditioning system plays an important role during the summer season. It keeps your home at a comfortable temperature and maintains a healthy indoor environment. However, if you notice unusual odors emanating from your AC unit, it's important to address them promptly. In this blog, we will discuss four common odors emitted by AC systems – rotten eggs, moldy, burning smell, and a car exhaust-like smell. 

Rotten Eggs Odor


The presence of a rotten eggs smell in your AC system could indicate a natural gas leak. Gas leaks are dangerous and require immediate attention.
  • If you detect a rotten eggs odor, turn off your AC unit, open windows and doors to ventilate the area, and evacuate the premises.
  • Contact your gas company or emergency services to report the gas leak.
  • Once the leak is resolved, consult a professional HVAC technician to inspect and repair your AC system.
- Schedule regular maintenance checks for your AC system to ensure all components are in good working order.
- Install a carbon monoxide and natural gas detector near your AC unit to provide early warning in case of leaks.
- Always rely on licensed professionals and avoid DIY installations or repairs involving gas connections.

Moldy Odor


A moldy smell is often an indication of exactly that -- mold or mildew growth within your AC system. Moisture buildup or clogged drain lines can contribute to this problem.
  • Turn off your AC unit and check for visible signs of mold growth. If the issue is minor, you may attempt to clean the affected areas with a mixture of bleach and water. However, if the mold growth is extensive, contact a professional.
  • Ensure your AC's condensate drain line is clear of any obstructions. If necessary, clean or unclog the drain line to prevent moisture accumulation.
  • Replace dirty air filters to improve indoor air quality and reduce the risk of mold growth.
  • Consider installing a UV light system within your AC unit to kill mold spores and prevent their growth.
- Regularly clean and maintain your AC system to prevent moisture buildup.
- Ensure proper insulation and ventilation in your home to minimize humidity levels.
- Use a dehumidifier in areas prone to excess moisture, such as basements or bathrooms.

Something Burning Odor


If your AC unit emits a burning smell, it may indicate an electrical problem or overheating of certain components.
  • Immediately turn off your AC unit and inspect the electrical connections for any signs of damage, such as burnt wires or melting insulation.
  • If you identify any electrical issues, contact your HVAC company to repair or replace the affected parts.
  • Overheating may be caused by a dirty air filter or a malfunctioning blower motor. Clean or replace the air filter and have the blower motor inspected by a professional.
- Change your air filters regularly to ensure proper airflow and prevent strain on the system.
- Schedule routine maintenance checks to identify and address potential electrical or mechanical problems.

Car Exhaust-like Smell


An AC system emitting a car exhaust-like odor may indicate a refrigerant leak. Refrigerants, such as Freon, have a distinct odor that resembles automotive exhaust.
  • If you suspect a refrigerant leak, turn off your AC unit and contact your HVAC company immediately. Refrigerant leaks require specialized expertise and equipment to repair.
  • Do not attempt to handle refrigerant leaks yourself, as they can be harmful to your health and the environment.
- Schedule regular maintenance checks to detect and address potential refrigerant leaks early.
- Avoid tampering with your AC system or attempting to recharge refrigerants without professional assistance.


Understanding the common odors emitted by AC units and their causes is crucial for maintaining a safe and comfortable indoor environment. By promptly addressing these odors and implementing preventive measures, you can ensure the longevity and efficiency of your AC system. Remember, it's essential to rely on professional HVAC technicians for gas leaks or complex repairs to ensure your safety and the optimal functioning of your AC unit.
Contact ECI Comfort

If you live in the Delaware Valley/Greater Philadelphia area and would like to find comfort within your home, visit our website or give us a call at 215 - 245 - 3200  to learn more.

This entry was posted in Central Air Conditioning, Comfort Tips, Home Maintenance, Ductless, Air Conditioning

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