the left you can see a diagram of
how a kitchen extractor would be wired.
There is a switched/fused/spur that
leads to a connection unit.
A cooker hood should usually come
with a decent length of flex this
then should be connected to the connection
The wiring and the 4inch ducting
pipe is most likely hidden by the
extractor fans chimney which will
lead outside even though you could
get an extractor fan with a carbon
filter which will filter/clean the
air instead of releasing it outside.
Kitchen extractor fans/hoods should
get wired through the ring main in
the kitchen and via a fused, switched