What must precede and follow an evacuation message when it is issued?

When issuing an evacuation message within a fire alarm system, it is essential to precede and follow the message with a tone that consists of a minimum of 2 cycles. This requirement ensures that occupants can clearly differentiate the evacuation signal from other sounds in the environment, thereby indicating an immediate need to evacuate. The use of a tone before and after the message serves as both a signal and a warning, alerting individuals to pay attention to the instructions being given.

The rationale for requiring multiple cycles is to ensure the message is received effectively and to maintain a sense of urgency. A single cycle may not adequately capture attention or may be misunderstood, whereas two cycles create a more pronounced alert. Thus, the timing and clarity of the audio signal are crucial for safety and proper evacuation procedures.

This requirement aligns with fire safety codes and standards, which emphasize the need for clear communication in emergency situations to facilitate timely evacuation and minimize confusion among building occupants.