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).

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.

Baker Engineering and Risk Consultants, Inc. (BakerRisk®) and Daewoo Engineering and Construction Co. Ltd. (Daewoo) performed vented (i.e., partially-confined) vapor cloud explosion (VCE) tests with both propane and lean hydrogen mixtures. BakerRisk’s Deflagration Load Generator (DLG) test rig was used to perform the tests. The DLG test rig was designed primarily to produce centrally-peaked blast waves that are representative of VCEs suitable for blast loading test articles, but has also been used for vented deflagration testing.

This document applies to the recovery phase of a typical emergency management framework that includes planning, response, mitigation, and recovery. This document provides practical guidance with a checklist to help an organization recover from a hydrogen incident and return to normal operations after the event scene has been stabilized and returned to the organization by the incident commander. This document does not include activities related to the immediate emergency response and initial investigations performed by other entities.

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. 

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. 

Safe practices in the production, storage, distribution, and use of hydrogen are essential for the widespread acceptance of hydrogen and fuel cell technologies. A catastrophic failure in any hydrogen project could damage public perception of hydrogen and fuel cells. Given the nascent nature of the mobile hydrogen applications, incidents involving mobile equipment can have detrimental impacts for the public as well as stakeholders and project proponents who are committed to hydrogen’s use as a safe alternative energy resource. 

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 information in this document provides answers to the questions that were raised during the Center for Hydrogen Safety April 27, 2023 webinar. The Q&As are sorted by topic with the question number for reference. The Q&As are sorted by topic with the question number for reference. Redundant questions were deleted from the original list.