Corrosion of steel pipes and amalgamization of mercury to aluminum within cryogenic heat exchangers could cause expensive damage. Failure to remove much or all of such acidic molecules, mercury, and other impurities could result in damage to the equipment. The 'acidic' elements such as hydrogen sulphide (H 2S) and carbon dioxide (CO 2), together with oil, mud, water, and mercury, are removed from the gas to deliver a clean sweetened stream of gas. These gases have wide-ranging boiling points and also different heating values, allowing different routes to commercialization and also different uses. Other gases also occur in natural gas, notably CO 2. The gas extracted from underground hydrocarbon deposits contains a varying mix of hydrocarbon components, which usually includes mostly methane (CH 4), along with ethane (C 2H 6), propane (C 3H 8) and butane (C 4H 10).

The natural gas is then condensed into a liquid at close to atmospheric pressure by cooling it to approximately −162 ☌ (−260 ☏) maximum transport pressure is set at around 25 kPa (4 psi) ( gauge pressure), which is about 1.25 times atmospheric pressure at sea level. The liquefaction process involves removal of certain components, such as dust, acid gases, helium, water, and heavy hydrocarbons, which could cause difficulty downstream. Hazards include flammability after vaporization into a gaseous state, freezing and asphyxia. LNG is odorless, colorless, non-toxic and non-corrosive. It takes up about 1/600th the volume of natural gas in the gaseous state (at standard conditions for temperature and pressure). Liquefied natural gas ( LNG) is natural gas (predominantly methane, CH 4, with some mixture of ethane, C 2H 6) that has been cooled down to liquid form for ease and safety of non-pressurized storage or transport. Liquified natural gas ship at Świnoujście LNG terminal in Poland Not to be confused with liquefied petroleum gas nor with natural-gas condensate (natural gas liquids).

600 psi to kpa