Turn off the HVAC system at the thermostat and breaker
Remove and wash vent covers and return grilles
Vacuum visible dust from registers and openings
Seal off supply vents to prevent dust spread
Use a vacuum with a long hose and brush attachment
Clean as far into each duct as you can reach
Loosen debris with a soft brush
Vacuum loosened dust and debris immediately
Clean the blower compartment if accessible
Replace or clean the air filter
Wipe down accessible interior surfaces
Clean the return air duct first
Work on one vent at a time
Avoid using excessive moisture inside ducts
Avoid spraying harsh chemicals into ducts
Reinstall clean vent covers and grilles
Turn the system back on and check airflow
Schedule professional cleaning if there is mold, pests, or heavy buildup