If this is the first cleanup i don't recommend compressed air. If there is a thick dust clog in there, it may be moved between the palets of the fan and it gets stuck. And that shall fry the fan. Insead, take it apart and clean it with a brush carefully, and also change the thermal paste from the heatsink. I'm telling you this because i've had a case like this. Fan very dirty, cloged with a thick layer of dust like a piece of fur, owner blew it in the fan, fan stuck, fan fried, owner sad....