Humming from ideal icos fan

[Leejak]

Have an ideal icos boiler. When its been on for 10 mins or there abouts. It begins to hum quite loud as you can hear it from other rooms. After its hum for 10 to 20 mins it goes quiet again.
Thinking its the fan?

Is it dangerous to run like this?
And is there an easier fix than replacing the whole fan unit?

Many thanks to all who read and respond.

 

[thereisawizza]

I'd get a RGI to look at it, these boilers can melt themselves to death.......