Design Fire Experiments - Tall Fir Trees

A series of experiments are reported on the burning behavior of dry, 3 m to 6 m tall, Douglas fir trees. The measurements were conducted in the open under quasi-quiescent conditions. The global measurements reported include the transient, peak, and total heat release rates, the yields of CO and soot, the mass loss, and near and far-field heat fluxes. The appearance of the trees was captured by photogrammetry. The fires were documented by video cameras from several perspectives. Measurements of the heat flux to the surroundings from the specimens were used to estimate the radiative fraction of the fires.
The total heat release measured by calorimetry and the ideal heat release calculated from the product of the total mass loss and the heat of combustion were found to be in reasonable agreement. The ratio of the CO yield to the soot yield was measured as nearly constant over a wide range of total heat release rates. A first pass at a rescaling methodology is presented, which corrects the transient heat release rate for system time response. The results provide unique calorimetric data which can be useful for development of design fire scenarios by fire protection engineers.
Notes: The initial and final specimen mass is reported on a dry basis. The time response of the oxygen consumption calorimeter was a significant source of uncertainty for these fast growing fires and the peak heat release values are significantly underestimated. A detailed analysis of the response time effect can be found in Appendix E of NIST TN 2327.