10.6 MCI, Triage, and Hazmat Awareness

Big Incidents Require a System

A mass-casualty incident (MCI) occurs when the number and severity of patients exceed the resources immediately available — the exact threshold depends on the local system, but the concept is the mismatch between need and supply. The EMR mindset flips here: instead of pouring all care into the first patient found, the goal becomes the greatest good for the greatest number. That requires structure, communication, and triage.

Triage is the system process of sorting multiple patients by severity and survivability so limited resources reach the patients most likely to benefit. The first-arriving EMR's job is usually to size up, declare an MCI, give an early patient count and request resources, and begin triage — not to stop and fully treat one critical patient while others go unseen. Early, organized information lets command scale the response. If an early patient count proves wrong, you update command with the corrected number so resources can be adjusted; you do not keep working from a number you know is inaccurate.

START and JumpSTART Triage

The most widely used field triage tool in the U.S. is START — Simple Triage And Rapid Treatment — designed to sort each patient in about 30 seconds using RPM: Respiration, Perfusion, Mental status. The only treatments allowed during START are opening an airway and controlling major bleeding; you do not stop to provide ongoing care.

The four categories and the adult START logic:

First, direct anyone who can walk to a collection area (green). For the rest, check breathing: not breathing after you open the airway is black/expectant; breathing over 30/min is red. If breathing is under 30, check perfusion (radial pulse or capillary refill); absent pulse or refill over 2 seconds is red. If perfusion is adequate, check mental status; unable to follow simple commands is red, able to follow commands is yellow.

JumpSTART adapts this for children, using breathing as the cornerstone — an apneic child with a pulse gets 5 rescue breaths before being tagged, because pediatric arrest is usually respiratory.

Hazmat Awareness: Recognize, Isolate, Deny Entry

EMRs train to the awareness level for hazardous materials — meaning the job is to recognize a possible hazmat scene, protect themselves and the public, and summon specialized resources, not to enter and mitigate. The tunnel-vision trap is rushing toward symptomatic patients near a leak; doing so creates more victims and removes a rescuer.

The awareness-level actions are:

• Recognize clues — placards/labels, container shape, vapor clouds, unusual odors, dead vegetation or animals, and multiple patients with similar symptoms (a major red flag for a chemical or toxic exposure).
• Isolate the area and deny entry to bystanders and untrained responders.
• Position yourself uphill, upwind, and upstream of the release at a safe distance.
• Identify from a distance using binoculars and the Emergency Response Guidebook (ERG) to look up the material and initial isolation distances.
• Notify dispatch and request a hazmat team and additional EMS.

So when several people near a leaking container report dizziness and nausea, the correct first action is not to don exam gloves and start patient care inside the area — it is to stay out, move to a safe position, isolate the scene, deny entry, and call for hazmat resources. Routine EMS PPE does not protect against chemical or toxic atmospheres. Patients are decontaminated by trained crews before EMRs provide care in a safe zone. Recognizing the limits of your role here is exactly what the Operations domain tests: protect the public, communicate the scale, and bring in the right resources.

Zones, Decontamination, and Other Special Operations

Hazmat scenes are organized into control zones that the EMR must respect:

EMRs work in the cold zone, caring for patients after they have been decontaminated. You never carry a contaminated patient into the ambulance, because doing so contaminates the crew, the unit, and the hospital. The Emergency Response Guidebook (ERG) is the standard field reference: look up a placard number or material name to find hazards and an initial isolation distance to keep the public back.

Beyond hazmat, the EMR supports other special operations at an awareness level. In water, ice, confined-space, or technical-rescue situations, recognize that these require specialized teams and equipment — do not attempt a rescue you are not trained and equipped for, because untrained rescuers are a leading source of rescuer deaths. Around downed power lines or unstable vehicles, establish a safe perimeter and wait for the utility or rescue resource.

** Doing the greatest good for the greatest number sometimes means not rushing in — and the exam reliably rewards that disciplined judgment.