Field gas boosting is the process of boosting low-pressure gas from the wellhead to a high-pressure pipeline. The wellhead gas pressure, below atmospheric pressure or at a relatively low positive pressure, will require a vacuum pump or a low-pressure compressor to extract the gas and to boost it to 15 to 30 PSI above atmospheric pressure. A liquid ring vacuum pump or compressor is used as the first stage and then delivers the gas to the second stage high-pressure compressor. The high-pressure compressor, usually a rotary screw or reciprocating compressor, delivers the gas to a gas processing plant via a pipeline.