New York State Certificate of Competency (CoC) Class B Pyrotechnician License Practice Exam

Chain-fused mortar racks are built to fire shells in a controlled sequence along a fuse line. For 3-inch shells, the safe, standard maximum is fifteen shells per rack. Keeping to fifteen ensures the fuse length is adequate for proper ignition timing across all shells, provides enough clearance for operators, and minimizes heat buildup and the chance of misfiring or shell interference. Going beyond this limit risks overload of the rack, unreliable ignition, and increased hazard during the display. A smaller count would underutilize the rack's capacity, while a larger count would exceed safe design limits.