HAZWOPER guide · 2 min read · Updated 2026-11-03
Site Control and Work Zones: Exclusion, Contamination Reduction and Support Zones
Site control keeps people away from hazards and keeps contamination where it belongs. OSHA 29 CFR 1910.120(d) requires appropriate site control procedures before cleanup work begins.
Elements of a site control program
The site control program is part of the site safety and health plan and must include, at a minimum:
- A site map
- Site work zones
- Use of a "buddy system"
- Site communications, including alerting means for emergencies
- Standard operating procedures or safe work practices
- Identification of the nearest medical assistance
The three work zones
| Zone | Also called | What happens there |
|---|---|---|
| Exclusion zone (EZ) | Hot zone | Where contamination is or could be. Entry only in the required PPE, only by trained and authorized workers. Bounded by the hotline. |
| Contamination reduction zone (CRZ) | Warm zone | Transition area holding the decontamination corridor. Reduces the chance of spreading contaminants to the clean zone. |
| Support zone (SZ) | Cold zone | Clean area for the command post, first aid, equipment, vehicles and break areas. Located upwind of the exclusion zone. |
Workers enter and leave the exclusion zone through access control points, and exit always goes through decontamination. Zone boundaries are set from site characterization and air monitoring data and should be marked with tape, cones, signs or fencing.
Setting zone boundaries
- Use visual survey, air monitoring readings and sampling results from site characterization
- Consider wind direction, terrain, drainage, and how far vapors, dust and spills could travel
- Leave enough room in the CRZ for a full decon line and emergency access
- Put the support zone upwind and adjust zones if conditions change
The buddy system
OSHA defines the buddy system as organizing employees into work groups so that each one is designated to be observed by at least one other employee in the group. Buddies watch each other for signs of exposure or heat stress, help each other, check PPE integrity and get help in an emergency.
Communications
Exclusion zone work needs reliable communication: two-way radios, hand signals (especially when respirators make speech hard), air horns or sirens for evacuation, and a check-in/check-out log at the access control point so everyone is accounted for.
Frequently asked questions
What are the three HAZWOPER work zones?
The exclusion zone (hot zone), contamination reduction zone (warm zone) and support zone (cold zone).
Where should the support zone be located?
Upwind of the exclusion zone, in a clean area, with the command post, first aid, equipment and break areas.
What is the buddy system in HAZWOPER?
A system that organizes workers into groups so each one is observed by at least one other worker who can watch for problems and summon help.
This guide summarizes federal OSHA, Cal/OSHA and EPA rules for training purposes. It is not legal advice. Always check the current regulation text and your site safety and health plan.