What is an explosion?

In this paper we focus on the term “Explosion”, and its definitions from a societal, regulatory and scientific perspective. The experts involved in developing Regulations, Codes and Standards (RCS) are typically not combustion scientists. Conversely, combustion scientists are typically not involved in development of RCS. Yet, both sets of experts develop literature applicable to explosions. There are aspects, particularly related to the definitions associated with explosions, where improved consistency would be beneficial. We will demonstrate that these definitions are inconsistent. Of particular interest is how these definitions affect hydrogen technologies. This manuscript has its roots in combustion science and examines how the unique behavior of hydrogen in many circumstances motivates a closer look at relevant RCS definitions and terminology. l point out ambiguities and how these lead to confusion in supporting definitions, and to overly restrictive RCS for hydrogen applications. We will then suggest internally self-consistent terminology which can serve as a starting point to develop consistent RCS definitions and requirements. These will, in turn, improve public and first responder safety, protect capital investment, and enable cost effective deployment of hydrogen technologies.