1.1*Scope.
A.1.1 Natural gas is a flammable gas. It is colorless, tasteless, and nontoxic. It is a light gas, weighing about two-thirds as much as air. As used in the systems covered by this standard, it tends to rise and diffuses rapidly in air when it escapes from the system.
Natural gas burns in air with a luminous flame. At atmospheric pressure, the ignition temperature of natural gas–air mixtures has been reported to be as low as 900°F (482°C). The flammable limits of natural gas–air mixtures at atmospheric pressure are about 5 percent to 15 percent by volume natural gas.
Natural gas is nontoxic but can cause anoxia (asphyxiation) when it displaces the normal 21 percent oxygen in air in a confined area without adequate ventilation.
The concentrations at which flammable or explosive mixtures form are much lower than the concentration at which asphyxiation risk is significant.
NFPA 704 rating is as follows:
(1) Health — 0
(2) Flammability — 4
(3) Reactivity — 0
(4) Special — None
Cryogenic fluids are gases that have been liquefied by having their temperature brought below –130°F (–90°C). They are typically stored at low pressures in vacuum jacketed containers.
Some of the potential hazards of cryogenic fluids are the following:
(1) Extreme cold that freezes or damages human skin on contact and can embrittle metals
(2) Extreme pressure resulting from rapid vaporization of the fluid during a leak or release of the cryogenic fluid
(3) Asphyxiation resulting from a release of the cryogenic fluid that vaporizes and displaces air
Personnel handling cryogenic fluids should use the protective clothing proscribed on the material safety data sheet (MSDS). This clothing typically includes heavy leather gloves, aprons, and eye protection.
1.1.1 This code shall apply to the design, installation, operation, and maintenance of compressed natural gas (CNG) and liquefied natural gas (LNG) engine fuel systems on vehicles of all types and for fueling vehicle (dispensing) systems and facilities, and associated storage, including the following:
(1) Original equipment manufacturers (OEMs)
(2) Final-stage vehicle integrator/manufacturer (FSVIM)
(3) Vehicle fueling (dispensing) systems
1.1.2 This code shall apply to the design, installation, operation, and maintenance of LNG engine fuel systems on vehicles of all types, to their associated fueling (dispensing) facilities, and to LNG-to-CNG facilities with LNG storage in ASME containers of 100,000 gal (379 m3) or less.
1.1.3 This code shall not apply to those aspects of vehicles and fuel supply containers that are covered by federal motor vehicle safety standards (FMVSSs).
1.1.4 This code shall include marine, highway, rail, off-road, and industrial vehicles.
1.1.5 Where conflicts occur between provisions of this code and referenced codes and standards, the provisions of this code shall apply.
1.1.6 Where, in any specific case, different sections of this code specify different materials, methods, or other requirements, the most restrictive shall govern.
1.1.7 Where there is a conflict between a general requirement and a specific requirement, the specific requirement shall be applicable.
1.1.8 Manufacturer specifications shall equal or surpass the applicable requirements of this code.

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