An under-expanded hydrogen jet from high-pressure equipment or storage tank is a potential incident scenario. Experiments demonstrated that the delayed ignition of a highly turbulent under-expanded hydrogen jet generates a blast wave able to harm people and damage property. There is a need for engineering tools to predict the pressure effects during such incidents to define hazard distances. The similitude analysis is applied to build a correlation using available experimental data.

This report provides an evaluation by members of the Hydrogen Safety Panel (HSP) of the June 1, 2019 hydrogen release incident at the Air Products and Chemicals Inc. (Air Products) hydrogen trailer transfill (transfill) facility located in Santa Clara, California. This review was requested by the California Energy Commission (CEC) in May 2020 and examines data from Air Products, and the Santa Clara Fire Department to provide an HSP perspective on the incident cause, response, and recommended follow-up actions. 

Mixing of hydrogen into natural gas, as a means of mitigating environmental concerns associated with the use of fossil fuels, poses a question of performance of appliances designed for use with natural gas, when fuelled by blends of hydrogen and natural gas. This study examines the performance of space and water heating appliances fuelled by methane as a natural gas proxy, and methane/hydrogen blends containing up to 15% hydrogen.

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. 

The delivery hydrogen vehicle fire at Diamond Bar, CA.  The fire, response and after action summary

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.