Safety: frequently asked questions

Does LNG explode when it spills?#

Not as a chemical explosion. A spill can produce a rapid phase transition, a physical explosion from sudden vaporisation with no combustion, but ignition of the vapour cloud requires the right fuel-air mixture and a source, which is a separate and less immediate hazard.

Why is LNG vapour heavier than air right after a spill?#

Because it is extremely cold. Cold gas is denser than warm gas at the same composition, so vapour fresh off a spill sinks and spreads along the ground before it warms enough to become buoyant.

What is the flammable range for methane?#

Roughly 5 to 15 per cent methane in air by volume. Below that the mixture is too lean to burn; above it there is not enough oxygen. The hazard exists only within that band.

How is LNG different from an LPG or petrol spill?#

LPG and petrol vapours are heavier than air at ambient temperature because of their molecular weight, and they pool persistently. LNG vapour is heavier only while cold, then becomes lighter than air and disperses upward, which changes how the hazard evolves over time.

What actually causes injury or death in an LNG incident?#

Historically, thermal radiation from a pool fire or a vapour cloud fire, and asphyxiation in confined spaces where vapour displaces oxygen. Cryogenic contact burns are a further, more localised hazard.

From Why LNG behaves the way it does in an incident.

What is a rapid phase transition?#

A physical explosion, with no combustion, caused by LNG vaporising almost instantaneously when it contacts water under the right conditions. It produces a pressure wave capable of damaging nearby structures but at nothing like the energy of a chemical explosion.

Does a rapid phase transition require an ignition source?#

No. It is a purely physical event driven by the speed of vaporisation, which is why it can occur even when no flammable mixture has formed and nothing has ignited.

What is a pool fire?#

A fire burning above a pool of spilled LNG that has found an ignition source. It burns at the pool's edges as vapour rises and mixes with air, and it is the dominant hazard used to size exclusion zones around terminals.

Can both happen at the same spill?#

They are independent and do not typically occur together, because a rapid phase transition consumes the conditions that would otherwise let a pool form and ignite. Safety analysis treats them as separate scenarios rather than a sequence.

Why does thermal radiation matter more than the flame itself?#

Because radiant heat travels well beyond the visible fire and can ignite materials or injure people at a distance, which is what siting studies actually measure and limit.

From Rapid phase transition, pool fires and vapour dispersion.

What is the IGC Code?#

The International Gas Carrier Code, the International Maritime Organization's mandatory code for the design and construction of ships carrying liquefied gases in bulk, covering containment, materials, venting, cargo systems and crew protection.

Is the IGC Code the same for every ship?#

No. Requirements are graded by cargo hazard, so an LNG carrier's flammable, low-flashpoint cargo puts it in the most stringent ship type category, with correspondingly higher standards for containment and secondary barriers.

What is SIGTTO?#

The Society of International Gas Tanker and Terminal Operators, an industry association whose guidance on ship and terminal operations — mooring, cargo transfer, compatibility, emergency response — is followed as the practical standard even though it is not law.

Why does an industry body's guidance matter if it isn't mandatory?#

Because the IGC Code sets design requirements but says little about day-to-day operations, and SIGTTO's guidance fills that gap. Terminals, charterers and insurers routinely require compliance with it as a condition of doing business.

Do all countries enforce the IGC Code the same way?#

The Code itself is uniform under IMO conventions, but enforcement runs through each flag state and port state, so consistency in practice depends on how rigorously individual administrations apply it.

From The IGC Code and what SIGTTO does.

What determines the size of an LNG exclusion zone?#

Thermal radiation from a credible pool fire and the distance a vapour cloud could disperse while remaining flammable, both calculated for defined worst-case spill scenarios rather than for every conceivable failure.

Why do LNG terminals need so much surrounding land?#

Because the exclusion distance is set by fire and vapour physics, not by the size of the equipment. A modest facility can still require a large surrounding buffer if the modelled consequences reach far enough.

Are exclusion zone rules the same in every country?#

No. Methodologies, acceptable risk thresholds and regulatory processes vary significantly by jurisdiction, which is one reason similar-looking projects can face very different siting outcomes in different countries.

Can an exclusion zone shrink over time?#

Yes, if containment design improves — better bunding, smaller credible spill volumes, improved secondary barriers — the modelled distances can fall. Retrofit is expensive, so this mostly affects new designs rather than existing terminals.

Is exclusion zone size related to the terminal's capacity?#

Only loosely. It depends on the size of tanks and the credible spill scenario associated with them, not directly on throughput, so a small terminal with a large tank can have a bigger zone than a busier one with smaller tanks.

From Terminal siting and exclusion zones.

What is methane slip?#

The fraction of a gas engine's fuel that passes through unburned and exits with the exhaust, rather than being converted to carbon dioxide and water. It occurs mainly in engines that premix gas and air before ignition.

Why does a small amount of slipped methane matter so much?#

Because methane is a far more potent greenhouse gas than carbon dioxide over a short time horizon — commonly cited at around 80 times more potent over twenty years — so even a small leaked fraction can offset a meaningful share of the carbon dioxide saved by burning gas instead of oil.

Which engines slip the least?#

High-pressure diffusion-cycle engines such as ME-GI, where gas is injected after air is already compressed and burns as a diffusion flame rather than a premixed charge, leaving very little unburned.

Which engines slip the most?#

Lean-burn Otto-cycle engines that premix gas and air before ignition, including many dual-fuel medium-speed engines and, to a lesser extent, X-DF two-stroke engines, because premixed gas can sit unburned in crevices the flame does not reach.

Does methane slip happen anywhere else in the LNG chain?#

Yes. Fugitive emissions from valves, seals and vents at production, processing and transmission facilities are a separate and often larger source, and are harder to measure than slip from a specific, testable engine.

From Methane slip and the emissions argument.

What counts as a lifecycle emissions estimate for LNG?#

Greenhouse gas output at every stage from gas extraction and processing, through liquefaction, shipping, regasification and pipeline transport, to final combustion at the point of use.

Why does liquefaction show up so clearly in the numbers?#

Because it consumes 8 to 12 per cent of the feed gas as its own fuel, which is a large, well-defined and directly measurable energy cost compared with the harder-to-measure leakage elsewhere in the chain.

What is the single biggest source of disagreement between lifecycle studies?#

Upstream methane leakage at production and processing, because direct measurement is difficult, self-reported inventories have repeatedly been found lower than independent satellite and aircraft measurements, and leak rates vary enormously between fields and operators.

Does LNG have lower lifecycle emissions than coal?#

On most assessments, yes, for power generation, even accounting for a reasonable range of upstream leakage — coal's combustion emissions alone are high enough that gas usually wins unless leakage is unusually severe.

Does LNG have lower lifecycle emissions than piped gas?#

Generally no, because LNG adds liquefaction and shipping on top of production, so the same gas delivered by pipeline typically has a smaller lifecycle footprint than the same gas delivered as LNG, all else equal.

From Lifecycle emissions: the honest version.

Which chokepoints matter most for LNG?#

The Strait of Hormuz for Qatari exports, the Strait of Malacca for cargoes reaching north-east Asia, the Panama Canal for US Gulf Coast cargoes going east, and Suez with Bab el-Mandeb for Middle East to Europe voyages.

Does all LNG pass through a chokepoint?#

No. A cargo from the US Gulf Coast to north-west Europe crosses open Atlantic and passes none, which is a large part of why Atlantic supply is valued for its route security.

Why does the Panama Canal matter for LNG?#

It is the short route from the US Gulf Coast to Asia. Slot availability and draught limits determine whether a cargo transits it or takes the longer route via Suez or the Cape.

What happens when a chokepoint closes?#

Cargoes reroute, voyages lengthen, and effective fleet capacity falls because each ship spends longer at sea. Prices respond to the shipping shortage as much as to the supply itself.

Is chokepoint exposure the same as risk?#

No. Exposure says a route normally passes a point. Risk depends on whether alternatives exist, how much longer they take, and whether enough ships are available to absorb the extra voyage time.

From LNG and maritime chokepoints.