(55be) An Analysis of Case Studies and Current Literature Regarding the Deflagration-to-Detonation Transition (DDT) Phenomenon

Explosions are generally classified as either deflagrations or detonations. As discussed in the Society of Fire Protection Engineers Handbook (5th Edition), a deflagration occurs when the flame front is propagated at subsonic speeds by the heat release from chemical chain reactions. If the propagation occurs at supersonic speeds with a leading shock initiating combustion, it is a detonation. However, in some circumstances a deflagration-to-detonation transition (DDT) can occur. This phenomenon is not well understood, even amongst fire protection engineers and fire and explosion investigators.

Facility design, including life safety, is informed by the known risks. Because the risk of a DDT is not well understood, it may not be adequately considered in the design phase - and an unacceptable risk to both people and property may result. Similarly, when investigating an explosion incident, certain causation hypotheses may not be adequately considered because the potential for a DDT having occurred is not known.

The paper is a literature and case study review, summarizing the current research around DDTs, as well as discussing several incidents where a DDT is believed to have occurred. This includes the Buncefield, Jaipur, and Wenling explosions as well as several from the authors' own investigation experiences.

A meta analysis of the factors common to each DDT incident are reviewed and discussed, and recommendations made to reduce the risk of a DDT. The primary conclusion is that the risk of flame front acceleration leading to a DDT is reduced by reducing the congestion that leads to turbulence and subsequent acceleration. These same factors are discussed relative to post-blast incident investigation.