As the size of an incident grows, and as more resources are drawn into the event, the command of the situation may shift through several phases.
In events, both large and small, both specific member and ad hoc teams may work jointly in a unified command system.
Individual team members can be trained in various aspects of the response, either be it medical assistance/first aid, hazardous material spills, hostage situations, information systems attacks or disaster relief.
Ideally the team has already defined a protocol or set of actions to perform to mitigate the negative effects of the incident.
Predefined roles are typically filled with individuals who are formally trained and on standby at all times, during scheduled hours.