The pneumatic elevator is the third type and the most recent innovation. This giant polycarbonate tube with a separate tube inside for the cab works with air pressure, pretty much like those deposit tubes at the bank drive-through (although, thank goodness, you don't whiz through quite that fast). The 37-inch-diameter tube can be installed without any need to build a shaft or a machine room, so if you need an elevator in an existing home, this may be the one for you. It needs no machine room, as the pump box that runs the elevator is only 11 inches tall and the same diameter as the tube.
Although you don't have to build a shaft, so this is a pretty easy thing to install, you do need to have wide enough doorways to get the tube into your house. It requires a 39-inch-wide opening to go through, and most doorways are about 36 inches or less.