Skip Navigation

U.S. Department of Health & Human Services
Navigation to Home, Contact Us, Site Map, About REMM
Radiation Emergency Medical Management (REMM)
REMM Banner
Search REMM Web Site
What Kind of Emergency? Initial Event Activities Patient Management Algorithms Management Modifiers Tools & Guidelines

REMM Home Contact Us Site Map About REMM

You are here: Home > Describing an Incident

  Quick Links
Help on REMM
Diagnosis & Treatment
  Other Web Resources

Describing an Incident

Key definitions: incident vs. event

What is the difference between an event and an incident using current US terminology?

    • Event (planned event)
      • Examples: a scheduled nonemergency activity (e.g., sporting event, concert, parade, training exercise, large convention, fair, large gathering, etc.)
    • Incident (unplanned event)
      • Examples: An occurrence or event, natural or manmade that requires a response to protect life or property. Incidents can include major disasters, emergencies, terrorist attacks, terrorist threats, civil unrest, wild land and urban fires, floods, hazardous materials spills, nuclear accidents, aircraft accidents, earthquakes, hurricanes, tornadoes, tropical storms, tsunamis, war-related disasters, public health and medical emergencies, and other occurrences requiring an emergency response.
    • Source: Introduction to the Incident Command System (ICS 100.b), Student Manual, August 2010, (PDF - 8.99 MB). See glossary. This is part of the National Incident Management System (NIMS).

top of page

International Nuclear and Radiological "Event" (Severity) Scale (INES)

  • Developed by International Atomic Energy Agency (IAEA) and partners in 1990 and it has undergone revisions.
  • The diagram below is the current version.
  • Severity scale ranges from 1 (least severe) to 7 (most severe)
  • The severity of an event is about 10 times greater for each increase in level on this scale.
  • Events without safety significance are called "deviations" and are classified as Below Scale/Level 0.
  • See INES information
  • Note nomenclature difference between IAEA and US
    • IAEA nomenclature references "event".
    • US nomenclature references "incident" as in the NIMS.
  • Examples
    • IAEA characterized the March 2011 Fukushima Nuclear Accident in Japan as an INES Level 7 accident
    • IAEA characterized the 1986 Chernobyl nuclear reactor accident in the Ukraine as an INES Level 7 accident.

top of page

Incident's Phases and Timelines


US Department of Health & Human Services     
U.S. Department of Health & Human Services Office of the Assistant Secretary for Preparedness and Response National Library of Medicine