Confined Spaces

Manholes, tanks, vaults, crawl spaces, pits and silos can contain invisible deadly atmospheres. Many confined space deaths are would-be rescuers who rushed in to help.

• Construction
• General Industry

What is a confined space?

A space that is (1) large enough for a worker to enter, (2) has limited or restricted ways in or out, and (3) is not designed for continuous occupancy.

It’s a permit-required confined space if it also has one or more of:

• A hazardous atmosphere, or could have one
• Material that could engulf you (grain, sand, water)
• Walls that slope inward or a floor that narrows, which could trap you
• Any other serious hazard (moving parts, electricity, heat)

Permit entry basics

• A written entry permit signed by the entry supervisor
• Atmospheric testing before and during entry, in this order: oxygen (19.5% to 23.5%), flammable gases (below 10% of the LEL), then toxic gases (like H2S and CO)
• Ventilation as needed
• Isolation of hazards: lockout, blanking lines, stopping flows
• An attendant outside the space at all times, in contact with entrants
• Rescue arranged before entry: retrieval systems, and a rescue team that can respond in time

Roles

• Entrant: knows the hazards, uses equipment, communicates with the attendant, and gets out when told or when alarms sound.
• Attendant: stays outside, monitors entrants and conditions, keeps unauthorized people out, and summons rescue. Never enters to rescue.
• Entry supervisor: checks conditions, signs the permit, and ends the entry when needed.

Last updated: October 1, 2026