Byram's Fireline Intensity Multiplies Heat Yield, Fuel Consumed and Rate of Spread
Fireline intensity, defined by George Byram in 1959, is the rate of energy release per unit length of the fire front, written \( I = H \cdot w \cdot R \) and reported in kilowatts per metre. Here \( H \) is the fuel's heat yield in kilojoules per kilogram, \( w \) is the mass of fuel actually consumed in the flaming front per unit area in kilograms per square metre, and \( R \) is the rate of spread in metres per second. Values run from tens of kilowatts per metre in a gentle backing fire to tens of thousands in a running crown fire. Because the three factors multiply, intensity is sensitive to all of them: a fire in light fuel moving fast can be as intense as a fire in heavy fuel moving slowly. Two cautions matter: \( w \) is the fuel consumed in the flame front, not the total fuel load, and \( I \) is per metre of front, so it is not a fire's total power. After this Concept you can compute a fire's intensity from its fuel and its speed, and say which factor dominates.
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Fireline intensity, defined by George Byram in 1959, is the rate of energy release per unit length of the fire front, written \( I = H \cdot w \cdot R \) and reported in kilowatts per metre. Here \( H \) is the fuel's heat yield in kilojoules per kilogram, \( w \) is the mass of fuel actually consumed in the flaming front per unit area in kilograms per square metre, and \( R \) is the rate of spread in metres per second. Values run from tens of kilowatts per metre in a gentle backing fire to tens of thousands in a running crown fire. Because the three factors multiply, intensity is sensitive to all of them: a fire in light fuel moving fast can be as intense as a fire in heavy fuel moving slowly. Two cautions matter: \( w \) is the fuel consumed in the flame front, not the total fuel load, and \( I \) is per metre of front, so it is not a fire's total power. After this Concept you can compute a fire's intensity from its fuel and its speed, and say which factor dominates.
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