Compressed Air and Vacuum Pumps
Compressed air is air which is kept under a certain pressure, usually greater than that of the atmosphere. Compressors are similar to pumps: both increase the pressure on a fluid and both can transport the fluid through a pipe. As gases are compressible, the compressor also reduces the volume of a gas. A vacuum pump is a device that removes gas molecules from a sealed volume in order to leave behind a partial vacuum.