The Development of Fire is predictable in an enclosed environment, like a room, and a normal fuel load. It is certain stages of development remains essentially the same even though it varies under different conditions and circumstances.
The beginning/Incipient stage
In the first few moments after the fuel source has been ignited, there is a localized flame and a free-burning open flame is usually the result. The room temperature remains around the same and the oxygen content of the room remains at approximately 21%. There will be a plume of hot gases, the hot byproducts of the flaming fire rising and a convective current will be set up with oxygen being drawn at the bottom of the flames. If there is a fuel, mainly a ceiling, on top of the fire, a V-shaped pattern will be produced with the flame spreading in an upward and outward direction. On the other hand, if there is very high ceiling, or no fuel above the flames, the hot gaseous byproducts will continue to rise until they cool to the ambient temperature and the smoke will diffuse into the air. The spread of fire will be initially by radiant ignition of nearby fuels and at this point, the environmental conditions as mentioned in the previous section will be the most significant at this point.
