There are several signs that your air ducts may have mold. The most common indicators include a persistent musty odor coming from your vents, especially when your HVAC system is running. You may also notice visible mold growth around vent openings or inside the ducts if you inspect them closely. Another sign is increased allergic reactions or respiratory issues among household members, such as sneezing, coughing, or nasal congestion, which can worsen when the system is on.

Mold in air ducts can lead to a variety of health issues, particularly affecting the respiratory system. Prolonged exposure to mold spores in the air can cause or exacerbate allergies, asthma, and other respiratory conditions. Common symptoms include coughing, sneezing, skin rashes, eye irritation, and nasal congestion.

Professional duct cleaning can effectively remove visible mold and contaminants from air ducts, but it may not always be a permanent solution unless the underlying cause of mold growth—such as humidity, moisture buildup, or leaks—is addressed. While professional cleaning can significantly improve air quality and reduce mold spores, preventive measures like sealing leaks, improving ventilation, and controlling indoor humidity levels are crucial for long-term prevention.

On average, a throughout professional air duct cleaning can take anywhere from 6 to 12 hours to complete for a standard residential home.