CPU fan on new 27"

Hi, I bought an 27" iMac from Apple 2 1/2 months ago, and most of the time it's very quiet. But sometimes the CPU fan gets very loud and the rpm is over 3,000. When it's quiet it's usually in the
938-940 range. I did a hardware test and there were no problems. Do I need to bring my Mac in, or am I missing something?

{quote:}1. Get a can of compressed air and make sure the vents on the bottom of the computer are not clogged with anything (do you have pets?).
2. Do the same for the circular vent behind the pedestal/base (above where the power cord enters the computer)
3. Do the same for the vent slit at the top of the back of the computer.{quote}
I would not clean the dust from my air intakes in that manner, because it will just blow the dust deeper into the iMac!
A better solution is to shut the iMac down, stopping the fans and then gently vacuuming out all the air intake ports.

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