The brickwork surrounding the firebox of a boiler is known as（）.

A.the accumulation of explosive gases
B.faster cooling of the fire
C.the fire to spread through the ventilation system
D.fixed foam systems to be ineffective

A.must be fixed if the vessel exceeds 12 meters in length
B.may be used as a fire pump
C.must be portable if there are more than 4 watertight compartments
D.must be capable of pumping at least 450 gpm

A.remove oxygen from the area
B.cool fuel below ignition temperature
C.smother with CO₂
D.smother fire with foam