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What is LNG?

Liquefied Natural Gas, or LNG, is defined as:


“Natural gas in liquefied form as a result of lowering the temperature to below its boiling point of approximately -162° Celsius (about -260° Fahrenheit)


LNG consists mainly of methane (CH4), with minor amounts of other hydrocarbons (ethane, propane, butane and pentane. By liquefying the methane gas, LNG takes up only 1/600th of the volume of natural gas in its gaseous state, which means the gas can be distributed around the world more efficiently. By comparison, compressed natural gas (CNG) takes up around 1/100th of the volume of natural gas in its gaseous state, depending on the actual pressure.


Main general physical and chemical characteristics of LNG




Molecular weight

16.0425 g

Density 6.67151E-4 kg/m3 (at 20° Celsius)
Boiling point -161.48° Celsius
Vapour density 0.55 (relative to air)


During transport the temperature should be below the boiling point.  Because LNG is extremely cold it requires special cryogenic equipment, procedures and training of the personnel involved. Due to the relatively low energy density of LNG (in MJ/l) it requires more onboard storage capacity than conventional fuels.

Fire hazard properties

The gas is flammable in volume concentrations between 4.5% and 16.5% in air, but auto-ignition only occurs at high temperatures.


Fire hazard properties of LNG and other fuels
Properties Petrol (100 Octane) Diesel


Methane (LNG)


Propane (LPG)
Flash point (°C) <-40 >62  
Flammability in air Lowest concentration in air (%) 1.4 0.6 4.5 2.1
Highest concentration in air (%) 7.6 7.5 16.5 9.5
Auto-ignition temperature (°C) 246-280 250-300 537 480

Further reading


The cryogenic characteristics of LNG may pose a risk to humans and materials if not handled carefully. If ignited, a gas cloud resulting from LNG release may lead to several types of fire or an explosion at flammable methane concentrations.