We clear the full run from the machine to the exterior hood, then confirm airflow at the outside vent. Usually done in under an hour.
US fire departments respond to thousands of home clothes-dryer fires a year, and failure to clean them is the number one cause.
A restricted vent traps the moist air the dryer is trying to expel, so clothes come out damp and the machine runs again.
Running hot against a blocked vent is what kills heating elements and thermal fuses early.
We measure at the exterior vent when we finish, so you know the whole run is clear — not just the first few feet.