CSIA Certified Dryer Exhaust Technician (C-DET) Practice Exam

What is a common sign that a dryer vent is blocked?

Prolonged drying times and unusually hot dryer operation. Normal drying times with cool operation. Drying times improve after a full cycle. Lint buildup on the exterior of the building.

Correct Answer:

Lint buildup on the exterior of the building.

Explanation:

Visible lint buildup around the exterior vent is a common sign that the vent is blocked because lint that should be exiting outside starts to escape and accumulate at the vent opening when airflow is restricted. When the duct is clogged, air can’t flow freely, so lint backs up and can spill out around the outside vent, creating a noticeable lint buildup. This is a direct, observable clue you can see from outside the building. While prolonged drying times or unusually hot operation can also indicate a blockage, exterior lint buildup provides a clear, tangible sign at the vent outlet. If you notice it, inspect and clean the exterior vent cap and the duct to restore proper airflow.

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