During mass casualty incidents, the demands placed on health systems outweigh available resources. The only way to ensure that the greatest number of patients survives is to prioritize who gets treated and evacuated first. This is accomplished by mass casualty triage where casualties are sorted by the severity of their wounds and assigned priorities for care and evacuation. Events such as hurricane Katrina, the Boston Marathon bombing, and the Pulse Night Club shooting have emphasized the necessity of having systems for sorting casualties. There are several primary triage systems in existence. In the United States, it is recommended that the primary triage system used meet, at a minimum, the Model Uniform Core Criteria.