Heating, ventilation, and air conditioning (HVAC) systems are central to indoor air quality. Older or poorly maintained systems can circulate mold spores, dust, and allergens throughout the home. Ask for maintenance records and check whether the unit has been serviced regularly. Newer systems aren’t always better if the ductwork is outdated or dirty.

Avoid homes where HVAC units are installed in garages or crawlspaces without proper sealing or elevation. These locations often expose the system to excess moisture and contaminants. Instead, seek systems installed in conditioned or semi-conditioned spaces with easy access for service and inspection.