Rattling noise from the fan

So my Lenovo laptop all of the sudden started making a very loud rattling noise when in use. I think that it's coming from the fan and Google tells me to clean it out. It sounds like something might be stuck in there, but i'm quite the amateur and therefore scared that i might just ruin something if i open it up. What to do? Is there anything i can do without compressed air?

The intake vent (or at least that's what i think it is) has this layer of grey, dusty felt that i can remove a bit of with a needle. But underneath i cant really see the fan, and that concerns me. Is that wierd layer of felt supposed to be there?

Please bear with my ignorance - I know that I'm quite possibly asking total noob questions :)