Kitchen electric fan roof light vent

[Carrerasax]

Help please
How do I remove this for cleaning.
There appears to be stews either side on the front edge to release cover from roof.
How does arm release though. No obvious screws and it seems pretty solid to just release by any clip.
Bessacarr Ducato 2017 if that makes any difference!!!!

 

[in h]

I think you undo the screws on the inside of the van. It'd not be very secure if you could remove it from the outside!

 

[Carrerasax]

It’s all covered up when it’s shut down!!!

 

[in h]

Nevertheless, the screws are inside.

 

[The laird]

What fan make / details are on the fan casing?

 

[Carrerasax]

Ohhhh, now your getting technical!!!

 

[The laird]

Is it fiamma omistor,or some other

 

[Carrerasax]

Is it fiamma omistor,or some other

I’ll check in the morning, Ta.

 

[Carrerasax]

Is it fiamma omistor,or some other

Hope this helps, pls don’t tell m I’ve got to go back up in the roof!!!!
Four screws in the corners inside appear to release the internal screen although I doubt this would come out without removing internal surround held with two further screws.
I just want to clean outer housing.
If I undo screws inside how do I remove the opening screw knob that will stop it coming apart? Do I just lever gently with a screwdriver?

 

[Carrerasax]

!!!!!!!