My stove fan vents straight back into the room. Anecdotally maybe 75% of friends whose stoves I've observed do the same thing.
It's a travesty as far as I'm concerned, but there you are.
(I live in an apartment; otherwise you can bet I would have done something about it before now.)
If you didn't check and put one yourself, you might not even have a carbon filter at all.
But in all cases this setup is totally insufficient for frying things without stinking the whole place.
Yes, unless you have equal amounts of outside air entering your domicile, a vent leading outside is not effective. A recirculating vent, however, still has a filter.
Hood filters capture airborne grease, smoke, steam, heat, odors, and other substances that are produced during cooking under the hood. Without the proper hood filter, your kitchen will be filled with airborne particles you don’t want your staff breathing! [0]
Not leading away moisture from the kitchen when cooking doesn't sound like a good idea to me but I'm just a child of a craftsperson working with these kinds of things, not one myself. Except if you live in like a hut with a lot of openings or something, but I'm kind of assuming this is about apartments and houses with isolation and so on.