To meet the requirement for the number of VDSs on board, what must be true about pyrotechnic VDSs?

The requirement for visual distress signals (VDSs) on board is crucial for safety while boating, especially for signaling for help in emergencies. Pyrotechnic VDSs, such as flares, are critical components that must be reliable and functional when needed.

To ensure these signals can effectively serve their purpose, they must not be expired. An expired pyrotechnic VDS might not work properly, thereby failing to attract attention and compromising safety. Maintaining unexpired pyrotechnic VDSs ensures that in an emergency situation, these signals can burn brightly and be visible from a long distance, effectively communicating the vessel's distress and attracting rescue efforts.

Certain other criteria for VDSs do not pertain to the functionality and safety of these signals. For example, VDSs are typically required to be stored in accessible locations to ensure that they can be quickly deployed in an emergency. Additionally, VDSs should not be reused after they have been activated; they are designed for single use only. Therefore, ensuring these signals are unexpired directly impacts their reliability.