The study found that 14 of the 70 California gas stations reviewed could readily accept hydrogen fuel, and that an additional 17 stations could accept hydrogen with property expansions, based on the National Fire Protection Association hydrogen technologies code that was published in 2011.

Under previous NFPA code requirements from 2005, none of the existing gasoline stations could readily accept hydrogen because the distances required in that code were larger and based on an “expert opinion-based process” that was developed for flammable gases in an industrial setting. The current code, known as NFPA 2, was developed with Sandia’s input and uses a “risk-informed process” as its basis.

Since all fueling stations are susceptible to fire, understanding how a potential hydrogen fire might behave was crucial to understanding and mitigating safety risks. As a result, researchers at Sandia spent years studying the intricacies of combustion engines and hydrogen behavior in order to develop a scientific basis for the separation distances listed in NFPA 2.

However, some gas stations may not be able to accept hydrogen under the new code because lot sizes vary greatly and many smaller sites, particularly those in dense, urban areas, cannot be configured properly, according to Chris San Marchi of Sandia. NFPA 2 indicates that fuel dispensers, air intakes, tanks and storage equipment must be certain distances from parking, public streets, on-site convenience stores and perimeter lines around the site.

San Marchi noted that for a “skinny” gas station or one sitting on a wedge-shaped lot, the required distance between a high-pressure tank carrying hydrogen and the property boundary would be too great. However, while larger lots naturally work better in the current environment, there are opportunities to develop risk mitigations that could allow even wider deployment of hydrogen fueling stations, he added.