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

Figure 182 shows the results for the first test run with the floor fan off. Several photoelectricalarm thresholds were reached between 200 s and 400 s. Around 800 s all alarm thresholds werereached, this corresponded to a transition from smoldering to flaming of the foam block. The airtemperature rose slightly until about 800 s where it rapidly rose by 10 EC following flaming ofthe foam. The flaming period was short lived due to the limited amount of material to burn, andthe temperature dropped over the next 100 s. The relative humidity dropped by about 5 %during the test. The mass concentration started to rise at 100 s, and by 250 s reached a localpeak of nearly 40 mg/m 3 . By 500 s it had dropped down to about 10 mg/m 3 , then started risingslowly again until 800 s when it rapidly shot up to a peak greater than 150 mg/m 3 . The numberconcentration started to rise at 100 s and by 300 s had reached a value of 1x10 5 particles/cm 3 ,and remained steady until 800 s when it rapidly increased to a value of 4x10 6 particles/cm 3 .The ionization chambers showed an increase of 0.1 V from 100 s to 200 s. They remainedunchanged until 800 s when they shot up rapidly by over 2 V.Figure 183 shows the results for the second test run with the floor fan off. Two photoelectricalarms reached threshold values before 200 s, but no other alarms did. The block of foaminitially smoldered vigorously, but as time went on, it apparently stopped. The test was stoppedat 800 s. The air temperature rise was on the order of 2 EC, while the relative humidity droppedby about 5 %. The mass concentration started to rise at 100 s and reached a nominally steadyvalue of 6 mg/m 3 at 400 s. The number concentration started to rise at about 80 s and reached amaximum value of 9x10 4 particles/m 3 by the end of the test. During the test, the increases in theionization chambers voltages were 0.2 V and 0.05 V for chamber 1 and 2 respectively.202