Have you noticed an unusual smell coming from your HVAC system – either from the unit itself or the vents? Until now the system has circulated clean, odorless air throughout your house.

You’re concerned and have questions. Does this smell indicate a problem? Is it a health risk? It’s not uncommon the first time your system is turned on for the season to have an odor. This is normal when switching from heating to air conditioning. Some bad aromas though require urgent attention. Here are four reasons why the HVAC system might be producing an unpleasant smell or stench.

Problem 1: Mildew or Mold

Have you noticed a musty smell emanating from your vents? It’s possible there is mold growth within the ductwork. There’s condensation within the unit, and when moisture doesn’t drain properly, it can migrate into the ducts and create mold growth. Moisture trapped in the AC unit can rapidly grow into harmful bacteria and distribute spores and mold while it runs. This not only creates an unpleasant smell throughout your home, it can also trigger allergies and worsen asthma symptoms.

Pro Tip: An HVAC professional can find the source of the buildup, clean it up, and ensure the unit provides clean air.

Problem 2: Burning Smell

Electrical odors are one of the most common, and worrisome HVAC smells. There could be a wiring issue, a circuit board malfunction, or your motor may be burning out. A dirty air filter can also restrict air flow and overheat electrical components. If the burning odor is continuous, it may indicate a mechanical issue with the AC fan or compressor.

Pro Tip: If you’re not a professional electrician, don’t try to fix the problem yourself! Turn off the AC unit and call your HVAC expert right away.

Problem 3: Refrigerant Leak

Are you smelling something like nail polish remover in your home air? Have you also noticed that your air conditioner is not cooling your home even though the fans are blowing? A refrigerant leak can create a smell like acetone that permeates your indoor air. If your system is old or hasn’t been properly maintained, the AC coil may have developed cracks or small holes. A refrigerant leak can decrease the performance of your unit, increase energy consumption, and release hazardous chemicals into the environment.

Pro Tip: If you suspect a leak, leave the inspection to professionals trained in safe refrigerant handling practices.

Problem 4: Rotten Smells

Rotten smells may be the result of dead rodents, lizards, birds, or other critters stuck in the air conditioning system. Over time, animals can decay and emit unpleasant odors. And turning on the AC discharges the foul smell into your home.

Pro Tip: A technician can locate the specific duct where the stench is and remove the critter, checking ductwork and sealing entry points.

Early detection and preventative maintenance are the best ways to avoid foul odors and keep your HVAC system running properly. Next time you smell an unpleasant odor in your home, call Bruce’s Air Conditioning & Heating at 480-968-5652.