Strange smells from your HVAC system aren’t just annoying — some can indicate safety issues. Here’s a quick guide to the most common odors we encounter in Houston homes.
🔥 Burning / electrical smell
Possible cause: Overheating motor, worn wiring, or a failing capacitor.
Action: Turn the system off immediately and call a technician. This can be a fire hazard.
🦠 Musty / moldy smell
Possible cause: Mold or mildew in the ductwork, on the evaporator coil, or in the drain pan. Extremely common in Houston’s humidity.
Action: Schedule a maintenance visit. We’ll clean the coil, clear the drain, and check for mold.
🥚 Rotten egg / sulfur smell
Possible cause: Gas leak. Natural gas is odorless, but utilities add mercaptan (rotten egg smell) as a safety measure.
Action: Leave the house immediately. Don’t flip switches or use your phone inside. Call your gas provider from outside.
🧦 Dirty sock smell
Possible cause: Bacteria buildup on the evaporator coil. Known as “dirty sock syndrome.” Common in humid climates.
Action: A coil cleaning during maintenance usually solves it.
🧪 Chemical / sweet smell
Possible cause: Refrigerant leak. Some refrigerants have a faint sweet or chemical odor.
Action: Call a technician. Refrigerant leaks need proper detection and repair — not just a “top-off.”