The liquefaction process of the natural gas includes removal of dust, acid gases, helium, water, and heavy hydrocarbons. The natural gas is condensed by cooling to −162 °C (−260 °F); with a maximum transport pressure applied at 25 kPa (4 psi).
In a typical LNG process, the gas is purified by removing water, oil, mud, and other gases. Trace amounts of mercury are also removed from the gas to stop mercury amalgamating with aluminium in heat exchangers. The gas is then cooled down in various stages until it is converted to a liquid.
LNG can be more volumetrically reduced than compressed natural gas (CNG). That is why LNG is more cost efficient to transport.