Macbook Air fan problem

Hi to all,

I need assistance with my macbook air mid 2011 model.

Years of usage and i faced no issue with my macbook air until recently it has developed a problem.

The moment i turn my macbook on, fan runs with full speed and it's quite audible and irritating at times. Even i close the lid, fan still runs at full speed.

This problem has aggravated with time. Earlier fan was loud only after using my macbook for 2-3 hours and then i just used to restart my laptop to solve the problem. However, at this moment fan turns on immediately when computer is turned on and remains constant on full speed, no solution from restarting.

I have read online and done SMC reset multiple times but no improvement in condition.

Please assist. Should i take my macbook to service centre or try to open it up to check for dirt.

Thanks in advance.