Performance of Home Smoke Alarms - National Institute of ...

Table 18 presents the results for the smoldering chair scenario. Estimates were made for threetests during the smoldering period. For a fixed location, the observed trend was that both thecount mean diameter (CMD) and diameter of average mass (Dam) increased as time increased.The exception to that trend was the estimate at 3000 s for SDC01, were the smoldering rate hadleveled off for a long period. The diameter of average mass estimates from SDC01 wereinconsistent with the count mean diameters. The most likely cause was a sampling bias wherethe room mass concentration was underestimated. Recall that during the manufactured hometests, the aerosol passed through the ionization chamber first, then it flowed to the TEOM. Itwas likely that a significant fraction of large particles were lost inside the ionization chamberand did not add to the mass concentration. The MOUDI size distribution measurement in theremote bedroom during SDC23 compares favorably with the den mean sizes estimated at 3000 s.Table 18. Estimated particle size from smoldering chair scenarioTestTime(s)NumberConc.(cm -3 )“Y”IonChamberMassConc.(mg/m 3 )CMD, Uc(μm)Dam,Uc(μm)SDC01 3000 21900 0.072 - 1.0, 0.2 -6400 8.02x10 5 1.55 5.35 0.64, 0.13 0.237000 5.21x10 5 1.55 10.5 0.93, 0.19 0.34SDC23 (den) 3000 35600 0.096 85.3 0.82, 0.16 1.7, 0.2(bedroom) 3000 64600 .017 - 0.08, 0.02 -3520 81300 0.032 - 0.12, 0.02 -SDC24 (den) 850 1.83e 6 .658 9.46 0.11, 0.02 0.21, 0.021110 99000 0.913 44.7 0.22, 0.04 0.41, 0.041400 25600 1.27 123.5 0.39, 0.08 0.62, 0.06Table 19 presents the results for a flaming chair scenario and a smoldering mattress fire after ittransitioned to flaming. The count mean diameter was computed using a chamber constant forflaming soot of 0.025 cm 2 [262]. Again, the mass concentrations for the manufactured home test(SDC02) were suspected to be low. Table 20 presents the results for the cooking oil scenario.After an initial increase in particle size, the count mean diameter remained relatively constantprior to ignition of the oil.The concentration and size distribution measurements provide a more fundamentalcharacterization of the smoke levels compared to the light extinction measurements. The datagathered here provide detailed information that may be used to help interpret the smoke alarmresponses observed in these tests, and to specify the smoke production rate and sizecharacteristics for modeling exercises.146