Annex A Explanatory Material
Annex A is not a part of the requirements of this NFPA document but is included for
informational purposes only. This annex contains explanatory material, numbered to
correspond with the applicable text paragraphs. A.1.1 This standard establishes essential requirements and standards for the design,
installation, and safe operation of liquefied natural gas (LNG) facilities. It provides guidance
to all persons concerned with the construction and operation equipment for the production,
storage, and handling of LNG. It is not a design handbook, and competent engineering
judgment is necessary for its proper use.
At sufficiently low temperatures, natural gas liquefies. At atmospheric pressure, natural gas
can be liquefied by reducing its temperature to approximately 260°F (162°C). Upon release from the container to the atmosphere, LNG will vaporize and release gas that, at ambient temperature, has about 600 times the volume of the liquid. Generally, at
temperatures below approximately 170°F (112°C), the gas is heavier than ambient air at
60°F (15.6°C). However, as its temperature rises, it becomes lighter than air. Note that the 260°F (162°C) temperature value is for methane. If the constituents are
present, see 3.3.15. For information on the use of LNG as a vehicle fuel, see NFPA 52, Vehicular Fuel Systems Code. A.1.3 Departure from the requirements of this standard can be considered by the authority
having jurisdiction on the basis of a risk assessment. In the case of such departures, approval
will be contingent upon a demonstration of fitness for purpose in line with the principles of