Mass casualty incident

A mass casualty incident (often shortened to MCI and sometimes called a multiple-casualty incident or multiple-casualty situation) is any incident in which emergency medical services resources, such as personnel and equipment, are overwhelmed by the number and severity of casualties. For example, an incident where a two-person crew is responding to a motor vehicle collision with three severely injured people could be considered a mass casualty incident. The general public more commonly recognizes events such as building collapses, train and bus collisions, earthquakes and other large-scale emergencies as mass casualty incidents. Events such as the Oklahoma City bombing in 1995 and the September 11 attacks in 2001 are well-publicized examples of mass casualty incidents.

A mass casualty incident will usually be declared by the first arriving unit at the scene of the incident. However, it may alternately be declared by a dispatcher, based on the information available from people who call their local emergency telephone number about the incident. A formal declaration of an MCI is usually made by an officer or chief of the agency in charge. Initially, the senior paramedic at the scene will be in charge of the incident, but as additional resources arrive, a senior officer or chief will take command, usually using an incident command system structure to form a unified command to run all aspects of the incident. In the United States, the Incident Command System is known as the National Incident Management System (NIMS). According to the Federal Emergency Management Agency, "NIMS provides the template for the management of incidents."

A size-up needs to be done by the initial person receiving an emergency call regarding a multitude of situations involving a mass amount of people or potentially involving a mass amount of people.

...
Wikipedia