People usually able to exhaust gas from a sealed container or container so that the number of gas molecules in the dwindling access to equipment or device called a vacuum pump. Currently in vacuum technology, using a variety of methods have been and can be obtained from the measured atmospheric pressure 105Pa to 10-13Pa, 18 orders of magnitude wide pressure range. Obviously, only one vacuum pump, to obtain such a wide low-pressure space of the gas state is very difficult.
     Access to technology in a vacuum, and vacuum technology currently used to obtain two ways, one is through this mechanism the motion of a gas discharge directly from a sealed container; the other is through the physical and chemical methods such as gas adsorption or condensation on cold surfaces.