Phases of fires in enclosures

Fire in enclosures may be characterized in three phases. The first phase is fire development as a fire grows in size from a small incipient fire. If no action is taken to suppress the fire, it will eventually grow to a maximum size that is controlled by the 

The fully developed fire is affected by (a) the size and shape of the enclosure, (b) the amount, distribution and type of fuel in the enclosure, (c) the amount, distribution and form of ventilation of the enclosure and (d) the form and type of construction materials comprising the roof (or ceiling), walls and floor of the enclosure. The significance of each phase of an enclosure fire depends on the fire safety system component under consideration. For components such as detectors or sprinklers, the fire development phase will have a great influence on the time at which they activate. The fully developed fire and its decay phase are significant for the integrity of the structural elements. 

Remote ignition. This is the sudden ignition by autoignition or piloted ignition, due to 

Rapid flame spread. As we know, radiant preheating of a material can cause its surface temperature to approach its piloted ignition temperature. This causes a singularity in simple flame spread theory that physically means that a premixed mixture at its lower flammability limit occurs ahead of the surface flame. Hence, a rapid spread results in the order of 1 m/s. 

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