Scene Size-Up and Safety: Hazards, BSI, and Scene Control

Scene Size-Up and Safety: Hazards, BSI, and Scene Control

Before you touch a single patient, you must answer one question: Is it safe to approach? Scene size-up is the structured process you complete from the moment you receive a dispatch to the moment you make patient contact. Skipping or rushing this step has injured and killed EMS providers. Your first and most important job is to go home at the end of your shift.

What Is Scene Size-Up?

Scene size-up is a continuous mental and physical assessment of everything around you. It begins with dispatch information and continues throughout the call. The core steps are:

1. Apply Body Substance Isolation (BSI) before leaving the rig or before contact.

2. Identify and control scene hazards.

3. Determine the mechanism of injury (trauma) or nature of illness (medical).

4. Estimate the number of patients.

5. Determine whether additional resources are needed.

None of these steps is optional. They overlap and repeat as conditions change.

Body Substance Isolation (BSI)

BSI is the assumption that all blood, body fluids, and moist surfaces are potentially infectious. Under the OSHA Bloodborne Pathogen Standard, EMS employers must provide appropriate personal protective equipment (PPE) and train employees in its use. As an EMT or Paramedic you are responsible for selecting the correct level of protection before patient contact.

BSI hierarchy — use the level the situation requires:

• Gloves — minimum PPE for every patient contact, every time.
• Eye protection (goggles or face shield) — required whenever splashing or spraying of blood or body fluids is possible (bleeding trauma, childbirth, airway management, suctioning).
• Gown — required when your clothing is likely to be soaked or heavily contaminated (major trauma, childbirth, extensive wound irrigation).
• N95 respirator — required for suspected airborne infectious disease (tuberculosis, certain respiratory illnesses as guidance directs). A standard surgical mask does not provide the same protection against airborne particles.

Put gloves on before you step off the unit. Add layers as the scene demands. Never remove PPE and re-approach without reassessing.

Scene Hazard Categories

Hazards fall into predictable categories. Train yourself to scan for each one on every call.

Traffic is one of the leading causes of EMS provider fatalities. Position the unit to shield the scene. Use traffic cones and warning lights. Wear high-visibility vests when working in or near a roadway. Never assume approaching drivers see you.

Fire and smoke require you to stage upwind and uphill. Never enter a structure fire. Fire suppression is the job of the fire service. Your role begins when the patient is removed to a safe area.

Hazardous materials (hazmat) demand recognition from a distance. Look for placards, labels, leaking containers, or patients with unexplained chemical burns or altered mental status. Stage well away from the hot zone, upwind and uphill. Do not enter without proper training and equipment. Call a hazmat team.

Violence includes domestic disputes, assault scenes, shootings, and crowd situations. Law enforcement must secure the scene before EMS enters. If a scene becomes unsafe after entry, leave immediately and wait for law enforcement — take the patient with you if possible but do not risk your own life.

Electrical hazards include downed power lines, damaged utility boxes, and flooded areas with energized equipment. Assume every downed line is live. Stay back at least the distance of one full span of wire. Only trained utility workers can make the scene safe.

Environmental and structural hazards include unstable buildings, confined spaces, swift water, ice, and extreme weather. Specialized rescue teams handle these environments.

Calling for Additional Resources

Early recognition of a complex scene saves time and lives. If you arrive and identify hazmat, multiple casualties, a structural collapse, or active violence, call for additional resources immediately — do not wait to see whether you can handle it alone. Resources you may request include: additional EMS units, law enforcement, fire suppression, hazmat team, air medical transport, or a medical incident command structure.

Scene Control and Staging

Stagging means positioning your unit in a location that is safe but allows rapid access when conditions change. Upwind and uphill is the rule for hazmat and fire. For violence, stage out of sight until law enforcement clears the scene. For traffic incidents, use the unit as a physical barrier between your crew and moving vehicles.

Once on scene, limit bystander access to the immediate patient area. Bystanders can contaminate evidence, introduce additional hazards, or interfere with care.

Continuous Reassessment

Scene size-up does not end when you reach the patient. Conditions change. A bystander may become agitated. A fire may spread. A second patient may be found. Assign one crew member to monitor the environment while the other provides care when staffing allows. Communicate changes to your partner and to dispatch.

Key Safety Rule

No patient is worth your life. An injured or dead EMS provider cannot help anyone. Retreat, request resources, and re-approach when it is safe to do so.