Flashover for bus fires from empirical equations

Flashover for local bus fires is discussed using the heat balance equation. Empirical equations on the air intake rates through the opening, heat release rate of the fire, and heat lost rate through the compartment wall are reviewed and applied. The possibility of flashover is studied by plotting the heat lost through the bus envelope and the heat generated by a fire against the air temperature rise in the bus compartment. The heat release rate curve of the fire was computed with the aid of a two-layer zone model. Heat losses through the bus envelope with different materials are compared. It is further confirmed that thermal conducting materials with higher heat loss would have lower chance to flashover.