How does a vacuum pump move gas from a low-pressure space to the atmosphere?

In the context of vacuum technology, a vacuum pump functions essentially as a compressor. Its primary role is to take in gas from a space where the pressure is lower than atmospheric pressure, mechanically increase the gas's pressure, and then discharge it into the atmosphere.1

Because gas occupies a much larger volume at low pressures, these pumps are often bulky. Depending on the specific design, they move gas through different mechanical methods:1

• Positive Displacement: These pumps, such as reciprocating piston or rotary-vane types, draw gas into a chamber during a suction stroke and then compress it by decreasing the chamber's volume until the pressure exceeds that of the outlet, allowing the gas to be discharged.12
• Kinetic/Ejector Methods: Devices like steam jet ejectors use high-velocity steam to transfer momentum to the gas, sucking it from the inlet line. The resulting mixture is then compressed as it passes through a diffuser, where kinetic energy is converted into pressure energy.1

By continuously repeating these cycles, the pump effectively moves gas from a low-pressure environment to the higher-pressure atmosphere.1