I am trying to make something similar to a venturi but it has to be passive to suck smoke out of the interior of a car when it is in motion. My idea is sort of centred round a venturi principle and I would mount it in a baffle that would be squeezed into a rear window by winding the window down a short way, insert the baffle and wind the window up. When moving the idea is that low pressure across the outside end of a pipe would encourage cigarette smoke to be drawn out of the tube and exhausted into the outside air. My wife smoke and we have a second job that requires us both to be in the car for longish periods and it is killing my sinuses! Would it be sufficient to mount a tube in my baffle that is squared cut at the end or should it be shaped and should my tube be tapered in any way?