Diversity vents are used to suck elements such as turrets out of a map. They were scrapped from the game as a testing element and were used instead as an updated version of the Vital Apparatus Vent, but the tools to make them remain.
This tutorial was written by Jessecar93 at 
Building a vent
First you need to make the vent that brings the elements out of the map. make a few prop_static's and search for tube in the model browser. Design a tube to fit your needs.
Where the vent exits the map, make a small room and fill the room with a trigger_multiple block. Add an output to it "OnStartTouch" -> "!activator" -> "Kill" Also remember to set the appropriate flags. This will remove items that touch it.
Making it suck
Fill the inside of all of your tubes with separate blocks of triger_push for each direction of the tube. For each of them set the force to 1500 and set the direction to the tube's direction. Also set the "physics objects" flag.
Sucking through portals
Under the base of the tube where the objects will fly in; place a point_push with an (X Y Z) of -90, 0, 0. Adjust the radius of so that the sphere will be just touching the top of the pipe, and set the magnitude to -40. This will automatically place a smoke effect on the second portal.