Same here; we have a gas stove and a useless range hood above it. I guess it's supposed to filter it? Or previous owner installed it just to skirt the requirements ;-<

In my experience, those are only effective as a grease trap, catching the aerosolized particles of cooking oil/fat.

Typically they have removable metal screens that can be cleaned.

Otherwise they do nothing to vent smoke or purify air.

It might have a carbon filter, which is pretty effective. Need to change it every few years though...

I've had that for two apartments in a row. The most it can do is direct fumes to the ceiling instead of in your face. Incredibly little effect, when I then need to had the windows open with a box fan for a few hours any time I pan-fry anything. It's very frustrating, as those fumes could have been caught and exhausted from the source with much less exchange of air.