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246 F I R E R E S E A R C H Wiersma, S . J . (Stanford Research Institute, Menlo Park, Cahforma) "Measure- ments of the Dynamics of Structural Fires," Annual Report, August 1971â August 1972, Defense Civil Preparedness Agency Contract DAHC-70-C-0219 Sections: D , G, I Subjects: Dynamic behavior of structural fires. Pulse of radiant energy. Burning rate. Maximum energy release, Volumetnc fire growth. Inflow winds. Ai r temperatures. Wood-frame structures. Carbon monoxide concentra- tions Author's Abstract The dynamic behavior of structural fires i n the context of civi l defense impbcations foUowmg nuclear attack is expenmentally evaluated Dunng the third year of the program, some gross variations in the structures were made. Measurements f rom all three years of expenments are used to evaluate the nature and magmtude of behavioral changes that result f rom vanations in both structural and environ- mental factors A simple empincal equation which fits reasonably well the pulse of radiant energy and the burning rate of a burmng building is used to generalize the dynamic char- acteristics of structural fires Quahtative observations are made of the dependence of two physically significant times, tmax, the time of maximum energy release, and te, a time charactenstic of the burmng time, which can be related to the fitting parameters of the equation on the structural and environmental variations. The volumetric fire growth is found to be exponential wi th time The intrastructure fire spread, as measured by the volumetnc doubhng time (VDT) increases wi th wind and addition of fuel to the rooms and decreases when ceilmgs are made non- combustible Three replications of the basic test condition give mean values and vanance expressed as standard deviation of Snax = 25 3 ± 2 6 min, <c = 19 7 ± 2 1 min, and F D r = 2 7 3 ± 0 22 mm Inflow mnds induced by the fires are small These results are consistent wi th estimates of air flow necessary for the measured burmng rates. Carbon monoxide and carbon dioxide levels and air temperatures all reach lethal levels wi th in a short penod of time after imtiation of the fire i n wood-frame struc- tures, usually corresponding to a point just pnor to flashover of the compartment. High temperature is usually the first lethal condition reached i n well-ventilated rooms, whereas in rooms wi th windows intact and the door closed, carbon monoxide concentrations usually become lethal before lethal air temperatures are reached
