Australasian Inter-Service Incident Management System (AIIMS) is the nationally recognised system of incident management for the nation's fire and emergency service agencies.
It was first developed in 1980's.

AIIMS is based on three key principles:

Management by objectives
Functional management
Span of control.

As you have asked about the span of control of Australasian Inter-Service Incident Management System (AIIMS), I am giivng you information about it, check below for the details

Span of control is a concept that relates to the number of groups or individuals that can be successfully supervised by one person.
During emergency incidents, the environment in which supervision is required can rapidly change and become dangerous if not managed effectively.
Up to five reporting groups or individuals is considered to be desirable, as this maintains a supervisor’s ability to effectively task, monitor and evaluate performance.
Where span of control is exceeded, the supervising officer should consider delegating responsibility to others.
Conversely, where the span of control is lower or the tasks are fewer (for example in a de-escalating incident), the supervisor may reassume responsibility or reorganise delegation to contract the structure to fit the tasks required.
The way in which AIIMS is "scalable" is that it does not require the full-scale response to every incident – it allows for the build-up of resources and response activity