Which device should not be used to fire concussion mortars or flash pots?

The correct answer reflects a critical safety principle in fireworks operations. Concussion mortars and flash pots are specialized devices designed to handle explosive effects under specific conditions. Using improperly rated or unsuitable devices to fire these pyrotechnic effects increases the risk of malfunction, unintended ignition, or failure to fire safely.

Converted electrical switch boxes, lamp sockets, and plug fuses each present potential hazards in this context. Converted switch boxes might not be designed to withstand the electrical load or environments associated with pyrotechnic uses. Lamp sockets are typically designed for low voltage and current applications and lack appropriate safety features necessary for firing explosive devices. Plug fuses may not provide the necessary protection or control mechanisms, exposing operators and spectators to danger.

For these reasons, it's crucial to use dedicated firing systems that are intentionally designed for handling the specific demands of firing concussion mortars and flash pots, ensuring both safety and reliability during operations.