Hi Jerry...As A guy who spent six years installing appliances for SEARS, I can assure you Range hoods are all provided with rotational blowers .What this means Jerry is that they can all and I am including Micro hoods here be rotated to be vented or ventless.
As far as your state ment about the filters which come with the units being for grease you are partly correct since some packaging includes both.
Jerry the reason I said I pull the filter if you reread what I said is that you can be sure that the charcol filter is behind it.
So next time you inspect one of these things make sure you check all of the above.
Now these new ventless dryers being made by Bosch.Oy that is another story.