What type of report do first arriving companies broadcast to incoming units?

The type of report that first arriving companies broadcast to incoming units is a size-up report. This report is crucial as it provides a comprehensive assessment of the situation on the ground, including the conditions present, the hazards involved, and the resources that may be required. The size-up report informs incoming units about the specifics of the incident, helping them to prepare and strategize their response effectively.

This initial communication establishes a foundation for coordination among the responding units, ensuring that everyone is aware of the situation and can act accordingly. It encompasses critical elements such as the type of incident, the current fire conditions, any life hazards, and the initial actions taken by the first arriving company. By providing this detailed assessment, the size-up report enables better decision-making and resource allocation during the emergency response.