Flashover is the rapid transition from a fire burning one object to a fire involving every combustible surface in the compartment. It happens when the hot upper layer becomes hot enough, conventionally around 500 to 600 degrees Celsius, to radiate roughly \( 20 \ \mathrm{kW/m^2} \) down onto the floor and furnishings, which is above their critical heat flux, so all of them pyrolyse and ignite within seconds. The transition takes only a few seconds and multiplies the heat release rate by a large factor, and no unprotected person in the room survives it. The rule this gives is a deadline: useful detection, alarm and escape must all happen before flashover, so the growth curve and the detector response time have to be measured against it. The confusion it resolves is thinking of a room fire as growing smoothly; it grows smoothly and then changes state. After this Concept you can identify the conditions that bring a compartment to flashover and place a detection deadline before it.
Flashover is defined as the transition from a localized fire within a compartment to a general conflagration in which all fuel surfaces in that compartment ignite at approximately the same time, and …