For how long should all on-scene apparatus sound air horns after notice of emergency evacuation?

The appropriate duration for sounding air horns after notice of emergency evacuation is 10 seconds. This specific duration is significant within operational procedures as it serves multiple purposes. Firstly, it ensures that anyone within the vicinity of the incident site clearly hears the evacuation warning, alerting them to immediately leave the area for their safety. A 10-second burst is long enough to grab attention, but not so lengthy as to cause confusion or panic.

In the context of emergency situations, effective communication can be critical in ensuring the safety of both personnel and civilians. By providing a consistent and recognized signal duration like 10 seconds, responders can establish a standard protocol that all crews understand and follow, enhancing overall situational awareness and safety.