How do pneumatic tubes work? — Barry, Northport, Ala.
Marshall Brain Answers:
Pneumatic tubes have a long history, and at one time were a technological marvel for sending messages and small packages, as described in this video:
Today this technology is alive and well, especially in hospitals, as demonstrated here:
To make it work you need a sealed tube. In the simplest system you need just one tube with one opening at the sending end and another at the receiving end. Imagine a vacuum cleaner at the receiving end as well, connected into the tube with a T connector, and a little door on the receiving end that keeps air out. When you turn on the vacuum cleaner, it will create suction in the tube. If you insert a capsule into the sending end, it will get sucked to the receiving end and drop out through the door.
In more advanced systems you would want to be able to send to multiple receiving stations, and things get a little more complicated, like this: