- Over time, various ways have been developed to describe mass casualty incident phases or timelines
- Descriptions vary by
- Venue: country, state, city, local, etc.
- Profession using the schema: e.g., fire and rescue, medical, legal,
- Type of incident: e.g., biological, chemical, radiation, natural disaster
- Purpose of the incident timeline: e.g., operations, medical late effects, hazardous waste disposal, environmental monitoring
- "Official" descriptions/diagrams of phases timelines have changed over time
- Below are two U.S. schemas