I am moving a kitchen sink to another inside wall and am wondering if I need a vent. In my mind, the main stack is the vent since it goes all the way to the roof. If I do need one, I recently saw a cap that goes on a vent pipe that allows it to be "vented" inside the cabinet. I think there was a filter on it. Does anyone know what I am talking about? BAsically I know it will be very difficult to access a vent if I move the sink. What are my options? Can I vent it to an outside wall or do I have to go to a roof?

Thanks for any advice!