Does anyone know of a microwave which has a built in hood underneath
it which filters the air properly please?

We have a GE setup with the microwave positioned over the cooker and a
fan in it with aluminium filters. As far as I can see, they feed the
air into ducts which must go behind the microwave and out through
vents at the top. No further filtering is done beyond the aluminium
filters?

They don't seem to filter much, especially as we tend to cook in such
a way as to give rise to quite a lot of smoke. Which tends to waft
all over the apartment before hopefully getting expelled out of
windows. Mind you, the filters do go black quite quickly, which I
take to mean that they are filtering something: I think that the
standard way of cleaning them is with baking soda?

I was wondering whether any other company had married up a microwave
to a fan effectively OR do the newer GE microwaves do any better a job
of sucking up the smoke and filtering it please?