This document provides an example safety plan in Attachment A associated with hydrogen and fuel cells, where there is a significant flammability or explosive hazard from quantities, pressures, exposures, or other conditions. Hydrogen is unique among flammable gases in that small quantities may result in ignition or explosions. This example safety plan was developed by Pacific Northwest National Laboratories (PNNL) and its Hydrogen Safety Panel (HSP) members to assist entities working with hydrogen to ensure the protection of life, property, and the environment.

The Hydrogen Safety Panel was established by the U.S. Department of Energy (DOE) to provide independent safety reviews and guidance to contractors in the DOE Hydrogen and Fuel Cells Program. In September 2017, the panel set up a task group to compile select hydrogen incidents from the H2Tools.org Lessons Learned database (https://h2tools.org/lessons) in a publication form for written reference, that are most pertinent to various types of DOE contractor projects. This report is the result of the task group’s work. 

Hydrogen Safety Panel, Safety Knowledge Tools, and First Responder Training Resources 

The ignition of a hydrogen-air mixture that has engulfed a typical set of ambient vaporizers (i.e., an array of finned tubes) may result in a deflagration-to-detonation transition (DDT). Simplified curve-based vapor cloud explosion (VCE) blast load prediction methods, such as the Baker-Strehlow-Tang (BST) method, would predict a DDT given that typical ambient vaporizerswould be rated as medium or high congestion and hydrogen is a high reactivity fuel (i.e., high laminar burning velocity).

Natural gas was first used as a vehicle fuel as far back as the 1930s. The first natural gas vehicles, which ran on uncompressed natural gas, were called “gas bag” vehicles and were used to combat gasoline shortages during World War I [1]. During and after World War II, compressed natural gas (CNG) vehicles using fuel tanks mounted on the roof gained popularity in France and Italy [2]. Today, there are more than 24 million CNG vehicles in service worldwide, including CNG buses that continue the early tradition of mounting fuel tanks on the roof.  

The HSP has reviewed many safety plans for gaseous hydrogen. An emerging trend is the use of liquid (cryogenic) hydrogen in the commercial market, potentially near residential areas, for fueling hydrogen fuel cell vehicles. Finding a “qualified” person to determine liquid hydrogen code compliance is difficult, and the skills necessary of such an individual are not well defined in the codes and standards.

Hydrogen Safety Panel, Safety Knowledge Tools, and First Responder Training Resources 

PNNL’s Hydrogen Safety ProgramWhy Hydrogen Fuel?Hydrogen – A Clean, Flexible Energy CarrierWhy Fuel Cells? H2@scale: Enabling Affordable, Reliable, Clean, and Secure Energy Across SectorsUpward trend with global fuel cell shipments 2018 U.S. Snapshot More details in Slides

Introduce the Hydrogen Safety Panel (HSP)Introduce key hydrogen safety resources that are availableOpen discussion on your hydrogen safety issues and needsExplore how the HSP can help the safe rollout of hydrogen and fuel cell technologiesIdentify projects that could utilize the HSP for impactful safety reviews

Ammonia and hydrogen represent opposite ends of the spectrum with regard to the potential blast loading resulting from an accidental vapor cloud explosion (VCE), although many in industry have expressed doubts as to whether either of these fuels actually pose a VCE hazard. Ammonia is some-times discounted as a VCE hazard due to the perceived difficulty in igniting an ammonia-air mixture and/or because of its low laminar burning velocity. Hydrogen is sometimes discounted as a VCE hazard due to the ease with which a hydrogen-air mixture can be ignited and/or because of its buoy-ancy.