As the upper part of a room becomes filled with very hot combustion products, this hot layer, like the flame itself, radiates energy to the fuel bed. The extra radiant heat makes the fuel burn faster than it would otherwise. Figure 2-2 is a schematic of a room fire, showing the development of the hot upper layer and the flow of hot and cold gases through a vent. This is the case for flaming fires, as well as smoldering fires, although the former are complicated by the hot- layer descent discussed above. The logic of the procedure, however, is the same.
Most real fires involve several items.
It also shows the buildup of temperature behind a wall of Run-in. These two curves are inputs Al and A2, respectively, for determining the smoke production rate of the room fire and the concealed combustible materials. It should be clear that the temperature in the room becomes untenable long before the region behind the wall warms appreciably. At some distance from the fire, the sole hazard of concern is the toxicity of the smoke. For the first 15 min or so, smoke issues only from the room fire.