Flame acceleration increases the hazard level or severity of a dust deflagration. Three consequences of flame acceleration are secondary explosions, confined flame acceleration, and pressure piling. Secondary explosions occur when fugitive dust deposits have accumulated on floors and other horizontal surfaces.
Flame acceleration effects are most pronounced when a combustible dust mixture is ignited at the closed end of a conduit and the deflagration is constrained to one-dimensional motion toward the open end. In this physical setting, the accelerating flame could potentially undergo a deflagration to detonation transition, a particularly powerful type of explosion. Pressure piling occurs when an explosion in one vessel is propagated via a conduit to a second vessel. The magnitude of the overpressure in the unburnt gas becomes increasingly larger as the flame accelerates. Methods for preventing or controlling flame acceleration effects will conclude this chapter.