After a radiological event — whether a dirty bomb, nuclear facility incident, or industrial accident — the contaminated zone requires orderly evacuation to minimise continued exposure. Unlike nuclear detonation fallout (where shelter-in-place is often the better initial response), radiological contamination zones from dirty bombs and industrial incidents often call for movement to clean areas as soon as possible.
Understanding the Contamination Zone
Zones Established by Authorities
Emergency responders will typically establish concentric zones around a radiological incident:
| Zone | Description | Who Is There |
|---|
| Hot zone (innermost) | Highest contamination; source vicinity | Emergency responders in full PPE only |
| Warm zone | Contaminated; requires decontamination on exit | Responders; evacuees being processed |
| Cold zone | Clean; decontamination point | Medical and emergency support; evacuees after decontamination |
| Evacuation zone | Broader area; precautionary | Residents directed to evacuation points |
The lines between zones are not always perfectly clear during a developing incident. Move away from the visible source of contamination and follow official guidance.
How Contamination Travels
Radiological particles from a dirty bomb:
- Are primarily deposited downwind of the explosion
- Concentrate in low areas (underpasses, basements, depressions)
- Stick to surfaces — pavement, clothing, skin
- Can be redistributed by foot traffic, vehicles, and wind
Before Evacuating
Before leaving a building in or near the contaminated zone, assess:
- Is your building itself contaminated? If it is clearly outside the visible contamination plume, it may be better protection than the street.
- Do you have respiratory protection? Put on an N95 or other mask before exiting.
- Do you know the evacuation route? Avoid areas that emergency broadcasts identify as contaminated.
If your building is in or near the contaminated zone:
- Close windows and vents before leaving to protect others who may shelter in place inside.
- Move with deliberate purpose — minimise the time spent in the contaminated outdoor environment.
Moving Through the Zone
Route Selection
- Follow official guidance first — emergency broadcasts will describe safe corridors and contaminated zones.
- Avoid the downwind path from the explosion or incident — contamination travels downwind.
- Avoid low-lying areas — underpasses, tunnels, subways, parking garages trap denser contamination.
- Use paved roads where possible — bare pavement contamination is lower than fields or disturbed ground.
- Do not take shortcuts through rubble or damaged structures — these have surface contamination and structural hazards.
Behaviour While Moving
- Move quickly but calmly — panic-running increases your breathing rate and therefore particle inhalation.
- Keep your mouth and nose covered — cloth or N95 throughout movement.
- Do not touch surfaces — walls, vehicles, railings may be contaminated.
- Do not eat, drink, or smoke until you are clear of the zone and have washed.
Vehicle Evacuation
If evacuating by vehicle:
- Close all windows and set ventilation to recirculate (not fresh air from outside).
- Drive out of the zone by the route indicated by authorities or the most direct upwind path.
- Park the vehicle outside the contaminated zone.
- Decontaminate before entering any building — your vehicle is now potentially contaminated.
- The vehicle itself will need professional decontamination before regular use.
At the Decontamination Point
Authorities will establish decontamination points at the edge of the warm zone. At these points:
- Follow all instructions from personnel — they have radiation monitors and can assess your contamination level.
- Remove outer clothing as instructed — even if you feel you were not heavily exposed.
- Proceed through the wash-down area — a supervised shower or wash station.
- Receive clean clothing — your contaminated clothing will be bagged and disposed of by authorities.
- Get medical assessment — even if you feel well; baseline documentation matters for future monitoring.
If no formal decontamination point has been established and you need to self-decontaminate:
- Remove outer clothing; bag and seal it well away from clean areas.
- Shower thoroughly with soap and water.
- Change into clean clothing from a sealed container.
- Report to the nearest medical facility or emergency services.
If You Cannot Evacuate
If evacuation is not possible (mobility limitations, routes blocked):
- Shelter in place — move to an interior room, close windows and vents.
- Signal for rescue — call emergency services; display a visible sign from a window.
- Stay low — if the structure is compromised, stay on the ground floor or basement.
- Await evacuation assistance from responders with appropriate equipment.
Quick Reference
| Stage | Action |
|---|
| Inside, zone not yet established | Close windows; await guidance; prepare to move |
| Moving on foot | Cover nose/mouth; avoid downwind/low areas; don't touch surfaces |
| Vehicle | Windows closed; recirculate air; decontaminate before entering buildings |
| At decon point | Follow all instructions; remove clothing; shower; medical assessment |
| Cannot evacuate | Shelter in place; signal rescuers; stay away from windows |
| After clearing zone | Wash thoroughly; report to medical even if asymptomatic |