When should a mortar be marked to indicate the presence of an unfired shell?

The correct approach is to mark a mortar immediately after an unfired shell is detected. This practice is crucial for safety and ensuring that personnel are aware of any potential hazards that may arise from unfired shells. By marking the mortar promptly, it communicates the presence of the unfired shell to all operators and emergency personnel, allowing for appropriate precautions to be taken.

Timely marking also prevents accidental firing of the mortar and helps in the management of the situation, ensuring that procedures to mitigate any risks posed by the unfired shell can be effectively implemented. Clear communication of the risk is essential in maintaining a safe environment during a fireworks display, and immediate marking constitutes a critical aspect of that safety protocol.