Hello fellow community members

The fan(s) inside my laptop make an audible 'grinding' type noise when running at above normal speed. (The noise is reminiscent of a tiny insect flying around inside the laptop.) The laptop has not been dropped or received any hard knocks so I am wondering if this issue is something to do with the air ducts needing a cleaning. The only air ducts I see are underneath the base and in between the base and the screen sections. 

Q1. Has anyone else had a similar problem and what did you do to fix it?

Q2. Is it ok to blow compressed air into the air ducts or does that risk damaging components?

Q3. What do other owners do about fan cleaning as the case does not look like it is supposed to be opened by me and presumably invalidates the warranty if it is opened?

Thanks