Right, so lint builds up in your dryer vent over time, and that's a serious fire hazard. When lint accumulates, it restricts airflow, which causes your dryer to run hotter and longer - that heat plus the flammable lint is essentially a recipe for a fire. Beyond safety, a clogged vent also makes your dryer less efficient, so it takes longer to dry clothes and uses more energy. That's why professionals recommend cleaning it annually, especially if you use your dryer frequently.