Because of the potential wide area impact of an unplanned liquefied natural gas (LNG) release, the National Fire Protection Association (NFPA), and later the U.S. Department of Transportation, issued standards and regulations that included specific methodologies for analyzing the consequences of an accidental LNG release.

The concept of a “design spill” was defined to evaluate the consequences of an accidental LNG release, with particular attention to the influence of safety protective measures. In addition to specifying the magnitude of the unplanned release, the design spill also specified some of the parameters for estimation of the downwind LNG vapor dispersion and the extent of the radiant heat from an LNG pool fire. The “design spill” was an important concept because the LNG rules were the first (and still unique) to define “exclusion zones” for purposes of establishing the allowable sites for establishing LNG facilities.

This paper identifies the hazards associated with LNG use, discusses the development and use of the “design spill” concept, and identifies problems with this approach. A detailed historical review of the regulations, codes, and standards applicable to LNG facilities is also provided. Changes and modifications in these codes in the past few years have caused considerable confusion. Thus, a complete review and revision of the “design spill” concept is required. © 2005 American Institute of Chemical Engineers Process Saf Prog, 2005