Maximum load-loss rate within the combustion zone of a vertically (downward) spreading fire was obtained for excelsior (0.07 cm in cross-section) at bulk densities from 0.0016 to 0.026 g/cm. Fuel was contained within a continuously weighed circular wire mesh basket 1 ft (929 cm) in circular area and 0.5 ft (15.2 cm) deep, surrounded by a separate annular basket of fuel, to minimize edge effects. Load-loss rates were similar to those obtained by Rothermel (1972) for horizontally spreading fires in the same fuel at the same bulk densities. The peak rate of load loss per unit, area exhibits a strong dependence upon bulk density for both vertically and horizontally spreading fires. The maximum of this peak rate occurs at the same bulk density in the two cases. Because of these similarities, this method offers an alternative for investigating the combustion dynamics of fire; moreover, the vertical array is much easier to use than the horizontal array.