The ignited fire sources in Test 3 are positioned under the S2 and
S4 sprinklers; the ignited fire source in Test 5 is directly beneath the
S1 sprinkler. From the heat release data (Fig. 9(c) and (e)), it is clear
that the fire in Test 5 features shorter initial and growth periods.
The fire in Test 5 spreads to the surrounding wooden cabinet (near
the northwest corner), which then ignites and generates radiation
feedback to the ignition source, further encouraging the fire’s
growth. The sprinklers above the ignition source are affected by the
heat of the fire source as well as by the heat from the burning wall
furnishings. Thus, the actuation time in Test 5 is shorter than that in
Test 3.