This problem occurs with a lot of notebooks. The cooling module attached to the processor gets clogged with fine dust and lint. The processor heats up quicker and the system turns the fans on high speed a lot more often and for a longer period of time. You should open up the computer and blow it out from the inside back through the air outlet. Otherwise you will be blowing the dust back into the computer. If it is clogged you will get a pretty big cloud of dust so do it somewhere where you wont get yelled at.