Your clothes dryer is an appliance you usually don't give much thought to, until something goes wrong with it. If your dryer starts to malfunction by operating more noisily than usual, or by taking longer than usual to dry your clothes, or if your clothes are still too damp at the end of the cycle, you need to check your dryer vent. A stopped-up vent can cause these symptoms, and can also lead to premature failure in major components of your dryer. Replace a flexible plastic vent, if you have one, because it reduces airflow and can easily be pinched shut. Check at the vent connection at the back of the dryer and at the exterior vent cap for lint, bird nests, or other obstructions blocking the airflow, and vacuum the vent out. If your vent is clear, or clearing it doesn't solve the problem, it's time for a service call by a reputable appliance repairman. It's sometimes only a simple and inexpensive part that needs replacement, but he's the one to make that call.