HazMat Symbol Recognition for Evacuation Safety

Find red/white/blue/yellow diamond-shaped signs on buildings, storage containers, or chemical facilities. The diamond is divided into four squares. Read from top to bottom: health hazard (blue), flammability (red), reactivity (yellow), special hazards (white). Numbers range from 0–4; higher numbers = greater hazard.

NFPA diamonds are posted on hazardous material storage sites. If you see one near your location, assume chemical/biological contamination is possible.

Blue (Health): 0=no hazard, 1=mild, 2=moderate (hospital care needed), 3=severe (life-threatening), 4=extreme (fatal/deadly). Red (Flammability): 0=not flammable, 1=high ignition temp, 2=ignites at elevated temp, 3=ignites at room temp, 4=extremely flammable. Yellow (Reactivity): 0=stable, 1=unstable if heated, 2=violent reaction with water, 3=violent explosive reaction, 4=extreme explosion risk. White (Special): OX=oxidizer, W=water reactive, SA=asphyxiant.

Hazards stack. A 4-3-2 diamond means fatal health effects plus highly flammable plus reactive. Evacuate immediately.

UN placards are diamond-shaped stickers on trucks, trains, and shipping containers. Top section shows class number (1–9); bottom shows UN identification number (4-digit code). Class 2=gases, 3=flammables, 6=toxins, 7=radioactive, 8=corrosives. Colors indicate hazard: red=flammable, yellow=oxidizer, green=non-flammable gas, white/black stripes=poison.

Any vehicle marked with a UN placard may be leaking. Avoid the transport route and warn others immediately.

Biohazard symbol: Three interconnected circles with center circle (trefoil), black on yellow/orange background. Indicates biological contamination, pathogens, or infected materials. Radiation symbol: Three-bladed propeller (trefoil), black on yellow background. Indicates radioactive materials. Both symbols warn of invisible, life-threatening hazards you cannot see or smell.

Do not touch anything marked with biohazard or radiation symbols. Invisible contamination can cause severe illness or death.

Toxic gases: evacuate 1–2 km upwind. Flammable liquids/gases: 300–500 meters. Radioactive materials: 500 meters–1 km; shelter indoors. Biological agents: treat as CBRN incident—evacuate 1+ km and shelter if downwind. Corrosive chemicals: 300 meters, avoid runoff zones. Always move perpendicular to wind direction first, then move upwind and uphill from the hazard zone.

Evacuation distances vary by container size and weather. When in doubt, move 1 km away, assess wind direction, and assume worst-case exposure.