Damage to buildings, equipment and people can result from a large-scale, short-duration deflagration.  The potential damage is primarily a function of the total amount of fuel burned in the event (total energy available), the maximum reaction velocity that is achieved, and the manner in which the expansion of the combustion gases is contained. Vented deflagrations tend to be less violent or damaging than contained deflagrations.
In free-air deflagrations, there is a continuous variation in deflagration effects relative to the maximum flame velocity.  When flame velocities are low, the effect of a deflagration is to release heat, such as in a flash fire.  At flame velocities near the speed of sound, the energy released is in the form of pressure, and the resulting high pressure can damage equipment and buildings.