What is the correct order of the four fire development stages?

• A. Incipient, Growth, Fully Developed, Decay
• B. Growth, Incipient, Fully Developed, Decay
• C. Incipient, Decay, Growth, Fully Developed
• D. Decay, Incipient, Growth, Fully Developed

Answer: (A)

Fire development moves from ignition to cooling, passing through stages that describe how the fire grows and then dies down. In the incipient stage, ignition has just started and the fire is small and localized, making early detection and suppression most effective. As the fire consumes more fuel, it enters the growth stage, with flames spreading, heat release increasing, and more of the room involved. When enough fuels are burning and heat buildup is extreme, the fire reaches the fully developed stage, where there is maximum heat and all available fuels in the space are actively burning. Finally, as fuels are exhausted or ventilation changes reduce heat output, the fire enters the decay stage, with burning decreasing and temperatures dropping, though hotspots can remain.

This sequence—incipient, growth, fully developed, decay—best matches the real progression of a fire. Other lists place stages out of order, implying the fire ends before it fully develops or skips the growth phase, which doesn’t align with how fires actually grow and then wind down.