If you see smoke or fire
Leave the area and call emergency services. A dryer vent service line is not emergency response.
Vent-related causes to investigate
Heavy lint, a crushed transition, a blocked exterior hood, a bird or pest obstruction, or a damaged long run can reduce exhaust airflow and increase heat.
Do not assume the vent is the only cause
Electrical, heating-element and other appliance failures can also create odors or heat. A useful assessment separates the exhaust path from appliance-repair needs.
Service note: The assigned provider confirms the actual cause, access, scope, price and schedule before work begins.