Overview

The first of the major hazards in a process plant is fire. Fire in the process industries causes more serious accidents than explosion or toxic release, although the accidents in which the greatest loss of life and damage occur are generally caused by explosion. Fire is normally regarded as having a disaster potential less than explosion or toxic release. One of the worst explosion hazards, however, is usually considered to be that of an explosion of a vapour cloud that has drifted over a populated area, and in this case the difference in the number of casualties caused by a flash fire rather than an explosion in the cloud may be relatively small.

Fire is, therefore, a serious hazard. The Second Report of the Advisory Committee on Major Hazards (ACMH) (Harvey, 1979b) refers in particular to vapour cloud fires and to the description of fires given by V.C. Marshall (1977a):

It can be said that such clouds will start to burn around their outer envelopes and will lift off to form fireballs. Such fires are dangerous in the extreme. When formed of hydrocarbons, they are luminous and radiate heat which can cause fatal burns to bystanders and ignite wood and paper; for example, they have been known to set fire to the interior of office blocks. As fireballs rise they produce mushroom clouds, in the stalks of which are formed violent upward convection currents that can suck up and ignite debris, and scatter burning brands over a wide...