Fan of laptop running at full speed even when not playing games

hello friends,need some help here.From past few weeks my laptop's fan is running at high speed even when i'm not doing any heavy work.Earlier warm air used to come out only when playing games.But now even while watching videos my laptop's fan start running at high speed making heavy noise & giving out warm air.Sometimes it does so even when i'm doing nothing.
Please help.

You can check if variable fan speed is working, monitor temps using Speedfan.