Site Control
The three zones
Site control physically separates clean from contaminated areas. The Exclusion Zone (hot zone) is where contamination exists and the highest hazard is present; only trained, PPE-equipped personnel enter. The Contamination Reduction Zone (CRZ, warm zone) is the transition area containing the decontamination corridor; it buffers the hot zone from the clean area. The Support Zone (cold zone) holds command, staging, and administrative functions and is expected to be free of contamination.
Access and communication controls
The Contamination Reduction Corridor runs through the CRZ and is the only route in and out of the hot zone. A site entry log records everyone entering and leaving, and a buddy system is mandatory - no one enters the exclusion zone alone. Communication must be established before entry (radios, hand signals, air horns) and must work in an emergency. Physical controls include fencing, barricades, signs, and a controlled access point. The prevailing wind determines zone layout: the support zone goes upwind.
Traps in questions
- Placing decontamination in the hot zone - decon belongs in the CRZ.
- Placing the command post downwind of the exclusion zone.
- Forgetting that the buddy system and entry log apply to all entries, including short ones.
- Assuming zone boundaries are permanent - they shift with wind, weather, and work progress.
- Confusing the CRZ with the support zone; the CRZ is where decon occurs and is potentially contaminated.
Rule of thumb
Draw the site with the wind arrow first: exclusion zone at the hazard, CRZ downwind of it with the decon corridor, support zone upwind. If an option places people or equipment downwind of the hot zone, it is usually wrong.