Standards for firewalls may be based on their thermal response to a prescribed radiant heat flux. Consider a 0.25-m-thick concrete wall ( 2300 kg/m3, c 880 J/kg K, k 1.4 W/m K), which is at an initial temperature of Ti 25 C and irradiated at one surface by lamps that provide a uniform heat flux of q"s = 104 W/m2. The absorptivity of the surface to the irradiation is s 1.0. If building code requirements dictate that the temperatures of the irradiated and back surfaces must not exceed 325 C and 25 C, respectively, after 30 min of heating, will the requirements be met?