The Global Asset Protection Services (GAPS) standard was written 20 years ago for property loss prevention at crowded chemical plants and is intended for existing and new oil and chemical facilities to limit explosion over-pressure and fire exposure damage; thus, the purpose is different than NFPA 2. NFPA distances were based on studies from the 1960s as well as qualitative factors that were deemed successful based on applied experience over the years. A risk informed approach as described within Annex E of NFPA 2 was applied to GH2 separation distances in the 2011 edition. These were further revised in 2020. Similar changes as described in Annex N of NFPA 2 were applied to LH2 distances in the 2023 edition.

These distances are based primarily on hydrogen piping releases as a function of pipe diameter and pressure. Exposures were aggregated into three groups and separation distances applied to each as applicable based on unignited vapor clouds, radiation exposure from jet fires, and overpressure. It’s important to note that many facilities have site specific issues such as large quantities, confinement, and congestion, so it may be applicable to apply contemporary engineering models to fully assess risk.