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Frequently Asked Questions (FAQs)


1. What is LNG and what are some of its properties?

LNG properties are:
  • LNG (liquefied natural gas) is natural gas, primarily methane, which has been cooled to its liquid state at -260F (162.2C)
  • Liquefying natural gas reduces the volume it occupies by more than 600 times, making it a practical size for storage and transportation
  • LNG (the liquid itself) is not flammable or explosive
  • LNG vapor (methane) is colorless, odorless and non-toxic. Methane can become an asphyxiant when it displaces the amount of oxygen that humans need for breathing
  • LNG vapor (methane) typically appears as a visible white cloud since its cold temperature causes humidity in the air to condense
  • Cold LNG vapor (methane) is flammable when it occurs in a 5%-to-15% concentration air. Less air does not provide enough oxygen to sustain a flame, while more air causes the fuel to become too dilute for ignitionv
  • LNG vapor (methane) is not explosive in an unconfined environment
  • After LNG vapors (methane) become warmer than -160F (-106.7C), they become lighter than air and will rise and disperse rather than collect near the ground

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2. Where does LNG come from?

Indonesia, Algeria, Malaysia, Trinidad and Qatar are currently the leading exporters of LNG. Russia and Iran also have the greatest potential.

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3. How is LNG shipped?

LNG is shipped via:
  • Specially designed ships are used to transport LNG to U.S. import terminals. The ships can carry LNG over long distances and are constructed of specialized materials and equipped with systems designed to safely store LNG at temperatures of -260 F (-162.2C)
  • All LNG ships are constructed with double hulls. This construction method increases the integrity of the hull system, provides insulation for the LNG and provides protection for the cargo tanks in case of an accident
  • Three basic tank designs have been developed for LNG ship containment and transport: prismatic free-standing, spherical, membrane
  • The "International Code for the Construction and Equipment of Ships Carrying Liquefied Gases in Bulk" (Gas Tanker Code) and Coast Guard regulations require that LNG ships meet a Type IIG standard of subdivision, damage stability, and cargo tank location
  • LNG is also transported via truck. LNG tanker trucks typically carry between 10,000 and 12,000 gallons (38-to-45 m3) of LNG. LNG trucks are used to deliver LNG from its source to remote or satellite peak sharing facilities. LNG trucks are also used with portable vaporizers as a temporary supply of natural gas if normal supplies are interrupted or for peak sharing during abnormal winter conditions

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4. Where do ships unload LNG?

Ships unload LNG at specially designed terminals where the LNG is pumped from the ship to insulated storage tanks at the terminal. LNG is also converted back to gas at the terminal, which is connected to natural gas pipelines that transport the gas to where it is needed. Specially designed trucks may also be used to deliver LNG to other storage facilities in different locations.

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5. How is LNG stored?

LNG is stored:
  • At more than 100 US facilities, either for use during periods of peak natural gas demand or as a real-time source of natural gas (from marine imports). Most facilities were constructed between 1965 and 1975.
  • In double-walled, insulated tanks, at pressures only slightly higher than atmospheric pressure. The inner tank contains the LNG, while the outer tank contains the insulation and prevents any vapor (methane) from escaping
  • In facilities are required to have a dike or impounding wall capable of containing 110% of the maximum LNG storage capacity. In the unlikely event of a spill, this feature will prevent any LNG from flowing off of the site
  • Storage facilities also use advanced monitoring systems to immediately detect any natural gas leaks or fires at the plant
  • All LNG storage facilities must comply with DOT (Department of Transportation) Title 49 CFR Part 193 - Liquefied Natural Gas Facilities: Federal Safety Standards and NFPA (National Fire Protection Association) 59A - Standard for the Production, Storage and Handling of Liquefied Natural Gas.

Please visit our For Citizens LNG Overview page for similar LNG information and photographs.

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6. Why make LNG?

Cooling natural gas to -260F (-162.2C) changes it from a vapor into a liquid. This reduces the space natural gas occupies by more than 600 times, making it a practical size for storage and transportation.

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7. Is LNG explosive?

No, in its liquid state, LNG is not explosive. When LNG is heated and becomes a gas, the gas is not explosive if it is unconfined. Natural gas is only flammable within a narrow range of concentrations in the air (5%-to-15%). Less air does not contain enough oxygen to sustain a flame, while more air dilutes the gas too much for it to ignite.

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8. What are the public safety issues related to LNG?

Safety issues are:
Flammable Vapor Clouds
  • If LNG is spilled, the resulting LNG vapors (methane) will warm, become lighter than air, and disperse with the prevailing wind. Cold LNG vapor will appear as a white cloud
  • If a source of ignition is present where LNG vapors (methane) exist at 5%-to-15% concentration in the air, the vapor cloud will burn along a flame front toward the source of the fuel
  • To keep the public safe, vapor dispersion exclusion zones are calculated and plotted to determine how far LNG vapors (methane) could possibly travel from a storage facility and still be flammable. These zones must not reach beyond a property line that can be built upon
  • If LNG is spilled in the presence of an ignition source, a fire will result from the continuous evaporation of the LNG contained within the impoundment
  • Since this fire would burn with intense heat, thermal exclusion zones are also calculated and plotted to keep the public at a safe distance from possible heat exposure
  • "Liquefied Natural Gas Facilities: Federal Safety Standards" are found in Title 49 CFR Part 193 Leaving FERC (You will be leaving FERC's website)
Dispelling the explosion myth
  • LNG is not explosive. Although a large amount of energy is stored in LNG, it cannot be released rapidly enough to cause the overpressures associated with an explosion
  • LNG vapors (methane) mixed with air are not explosive in an unconfined environment

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Updated: May 30, 2012