This video provides instructions on how to clean air vents. It suggests turning off the computer, disconnecting external devices, using compressed air to blow out dust from the vents, and then reconnecting devices and restarting the computer.
How to clean air vents: To clean your air vents, turn off the computer. Disconnect all external devices. Unplug the AC adapter and remove the battery. Hold a can of compressed air at a 90-degree angle 6–8 inches away from the air vents and blow out any dust.
Reinsert the battery and plug in the AC Adapter. Make sure the computer is sitting on a flat surface. Finally, reconnect the external devices and restart the computer.