The discussion of what happens when there was a leak of liquid natural gas (LNG) from LNG terminal operations or from an LNG ship needs some clarification. LNG is primarily methane that is stored and transported in liquid form at a temperature of approximately −162 °C (−260 °F) i.e. very cold. Putting an ignition source into LNG is not a demonstration of its safety as there is no oxygen present to allow for burning. Flammability is the property that makes natural gas desirable as a heat and cooking source, and methane only ignites when it is a gas.
When there is an LNG release, the liquid is heavier than air and remains close to the ground. It is very cold and any living thing that it touches will freeze, much like if you plunge an object into liquid nitrogen. Next, the liquid violently boils and return to its gaseous state and forms a gas cloud. When this happens, it displaces any air in the area of release and suffocates anyone close to the leak.
It is when the natural gas cloud mixes with air that it becomes flammable. Then, if there is an ignition source, for example a spark from a motor, it will ignite, just like when you light your gas stove. Fire from this gas cloud creates a fireball, much like the effect of lighting your BBQ grill with a match on the third or fourth attempt, although a lot larger. It is not an explosion like a stick of dynamite, but a giant fireball that engulfs everything around it.
Page 4.7-3 of the 2015 Jordan Cove Environmental Impact Statement outlined what would happen if a gas leak occurred at the Jordan Cove terminal or from a disabled LNG ship in the channel. Any living thing within 0.3 miles of the accident, an area known as the blast zone, would not survive. Those living within one mile will receive second-degree skin burns after 30 seconds of exposure, and those within 2.2 miles, are still at risk of burns if they do not seek shelter.
Having a factual understanding of what happens when an LNG leak occurs is crucial to allowing people to determine whether they will accept those risks.