What is the term for a fire that requires firefighting activity from most or all personnel assigned to the alarm?

The term "working fire" specifically refers to a fire incident that necessitates the engagement of most or all personnel who have been dispatched to the scene. This indicates that the fire is significant enough in scale or complexity that the firefighters on the scene must actively participate in extinguishing the fire and managing the situation. A working fire typically involves multiple units, additional resources, and coordinated efforts to control and mitigate the fire hazards effectively.

The use of this term helps to communicate to responders the level of response needed and ensures that the appropriate number of personnel and equipment are available to tackle the fire efficiently. It reflects not only the severity of the situation but also the response protocols which are designed to protect life and property during a fire incident.

Other terms such as "mega fire," "major incident," or "full response" may describe large-scale or multi-faceted emergencies but do not specifically align with the structure of fire service terminology regarding the direct involvement of personnel at the scene of a fire. Therefore, "working fire" is the most accurate designation in this context.