A fire department's training evolution often requires what safety measure?

Continuous supervision by officers is a vital safety measure during a fire department's training evolution. This supervision ensures that trained and experienced personnel are present to monitor the actions of trainees, provide guidance, and intervene if unsafe practices occur. The presence of officers helps maintain discipline and enhances the safety of training operations, as they can address potential hazards in real-time and ensure that procedures are followed correctly.

In contrast, while off-duty personnel can contribute to training efforts and external training facilities may provide valuable resources and different environments, these do not directly enhance safety during the evolution itself. Moreover, while humor may be beneficial in reducing stress and improving morale, it does not serve as a safety measure within the context of training operations.