There are now downdraft range vents being made by a number of
manufacturers, Kitchenaid, Broan, GE, etc, that pop up and are
typically used with island cooktops. They are similar in concept
to the original downdraft vents invented by Jenn Air. The Jenn Air
type place the downdraft opening in the middle of the range at the
surface, with a blower that pulls air down and vents outside. This
newer type go at the back edge of of the range and when not used, sit
flush to the counter. They are about 2" wide and the length of the
range (36"). When activated, the vent moves up about 8 inchs and
turns on, with a 600CFM blower venting the air outside. The idea
being that by being higher, they will be more effective at catching
smoke. You also don't lose any burner space, so you can have a std
36" 5 burner gas cooktop.

I'm considering one and wondering if anyone has any actual experience
with one. I know they won't be as good as a true range hood at
catching all the smoke, but wondering how much better, if any, they
are compared to the Jenn Air downdraft type which I presently have.
I could put in a regular overhead hood, but it would be a lot more
work, require tearing up ceiling, moving/adding recessed lights, new
holes through exterior walls, etc.