On the theory of flashover development

• Published in: Fire safety journal Vol. 25; no. 3; pp. 229 - 259
• Main Authors: Graham, T.L., Makhviladze, G.M., Roberts, J.P.
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 01-10-1995; Elsevier Science
• Subjects: Applied sciences; Building technical equipments; Buildings; Buildings. Public works; Exact sciences and technology; Fire protection; Script; Wall; Fire development; Flash over; Ignition; Fire; Thermal inertia; Theoretical study; Models; Time
• ISSN: 0379-7112
• DOI: 10.1016/0379-7112(95)00049-6

The characteristics of hot smoke layer development from ignition to flashover are obtained for a fire in a compartment with one opening. Flashover itself as a final stage of development is analysed using heat balance considerations for the developed hot layer (in direct contact with the external atmosphere through the opening) on the basis of a two-zone model and classical thermal explosion theory. Flashover is reasonably assumed to take place during the early development of the fire when the density and temperature of the lower zone may be taken to be close to their initial values. Critical conditions for flashover to occur are found in a general form in terms of the determining similarity criteria. The adiabatic flashover induction period in the absence of heat losses, which is a useful qualitative and quantitative characteristic, is given. Calculation of the flashover induction time allows for an evaluation of the total time for fire growth from ignition to flashover, with which we place the study of critical conditions in the context of the full fire scenario. The results obtained give simple but general enough formulae for representation of the flashover phenomenon.