Laptops rely on extremely compact cooling systems involving a fan and heat sink that can fail due to eventual clogging by accumulated airborne dust and debris. Most laptops do not have any sort of removable dust collection filter over the air intake for these cooling systems, resulting in a system that gradually runs hotter and louder as the years pass. Eventually the laptop starts to overheat even at idle load levels. This dust is usually stuck inside where casual cleaning and vacuuming cannot remove it. Compressed air can dislodge the dust and debris but may not remove it; once the device is turned on, the loose debris is reapplied to the cooling system by the fans. Instead, a complete disassembly is needed to clean the laptop. Many laptops are difficult to disassemble by the average user and contain components sensitive to electrostatic discharge (ESD).
Meaning that if a lot of dust is stuck, there isn't much chance of you just blowing it out, rather, dislodging it.
But I know many either cannot disassemble laptops due to the difficulty, and fear of damaging something, I assume you could just hold the fan of the intake vent and blow some air into there. Ensure the laptop is off, pull the battery out and charging lead.