National Fire Protection Association Standard for Gaseous Hydrogen Storage
by Neil Rossmeissl, Hydrogen Program Manager, U.S. Department of Energy


Fire and other safety codes determine critical aspects of siting for hydrogen storage at refueling stations. According to a study by Longitude 122 West, a “safety keep out” zone is specified and must be considered in the layout of system components for any fueling station. In North America, the fire codes established by the National Fire Protection Association (NFPA) are the most commonly used to determine safe practices. These safety zone requirements defined in the U.S. codes were published in the early 1960s. They could not be verified and are likely based on natural gas or other flammable gas experience. The distances published or proposed may be too conservative and may hinder the development of a hydrogen infrastructure. Without additional hard data, however, it is almost certain that changes in these requirements will not be accepted by the code organizations. 

The Department of Energy’s Hydrogen, Fuel Cell and Infrastructure Program decided to address this effort which would provide experimental data and verified simulations for new requirements that will enable the establishment of safe, validated minimum separation distances.

In November 2002, a meeting was held at the Sandia National Laboratories in Livermore, California to bring together participants from standards developing organizations, energy companies, government laboratories, and universities. The objective of the meeting was to finalize the existing tasks and identify new tasks.

The groups discussed the project and the range of potential experiments and modeling efforts that could be funded. It was decided to focus the project on providing basic properties of hydrogen and air mixtures with compressed hydrogen storage. There are three types of contact that objects might encounter when exposed to a hydrogen plume: flame impingement, heating due to radiation, combustible cloud contact. The likelihood and impact of each of these three types of contact can be determined with the following four methods:

• Experimentally measured flame impingement distances and various hydrogen flow rates and leak geometries
  
  
• Experimentally determined hydrogen flame radiation values
  
  
• Experimentally determined values for leanest ignitable hydrogen/air mixture
  
  
• Validated Computational Fluid Dynamics (CFD) model to predict hydrogen gas motion