Confined Space Definition
A confined space has three characteristics: large enough to enter and work, limited means of entry/exit, and not designed for continuous occupancy. Examples: tanks, vessels, silos, storage bins, hoppers, vaults, pits, manholes, tunnels, and pipelines.
Permit-Required Spaces
A permit-required confined space (PRCS) has one or more serious hazards: hazardous atmosphere, material that could engulf an entrant, internal configuration that could trap, or any recognized serious safety/health hazard. PRCS require a written permit, atmospheric testing, ventilation, and standby rescue.
Atmospheric Hazards
Test atmosphere BEFORE entry and continuously during work. Oxygen: 19.5–23.5% acceptable range. LEL (Lower Explosive Limit): below 10% of LEL acceptable. Carbon monoxide: below 25 ppm. Hydrogen sulfide: below 1 ppm (10 ppm IDLH). Use a calibrated multi-gas meter. Never rely on smell.
Roles & Rescue
ENTRANT: knows hazards, communicates with attendant, exits immediately when ordered. ATTENDANT: stays outside, monitors entrant and atmosphere, performs non-entry rescue if possible, calls emergency services. ENTRY SUPERVISOR: authorizes entry, verifies permit conditions. Non-entry retrieval systems must be in place.
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