The myth of episodic deflagration in large, unconfined vapor clouds

Abstract

Reports and reviews issued by the Health and Safety Executive (HSE) have a wide‐ranging influence that extends well beyond the United Kingdom. One such recent document, RR1113 Review of Vapor Cloud Explosion Incidents, discusses explosions arising from the ignition of large vapor clouds. The report proposes a mechanism called “Episodic Deflagration” which has been proposed as an alternative to Deflagration to Detonation Transition (DDT). Here, we examine the concept and the assumptions behind this mechanism in detail. We examine fundamentals purported to characterize this mechanism such as the so‐called cumulative build‐up of pressure over time, an assumed stationary flame state and the radiant heating mechanism proposed as the basis for this postulated phenomenon. We show that the concept is fundamentally flawed and built on unrealistic assumptions, leading to the conclusion that this phenomenon should be ignored.