OSHA Confined Space Entry: Permit, Atmospheric Testing, and Rescue Mistakes

29 CFR 1910.146 · Permit-Required Confined Spaces

Keywords: confined space entry permit, permit-required confined space, atmospheric testing order, confined space rescue, entrant attendant entry supervisor, OSHA 1910.146, non-entry rescue

Permit-Required vs. Non-Permit Space

• A confined space is: large enough to enter and perform work, has limited means of entry/exit, and is not designed for continuous employee occupancy.
• It becomes permit-required if it has: a hazardous atmosphere, material that could engulf, internal configuration that could trap, or any other recognized serious safety hazard.
• A permit space can be reclassified as non-permit if all hazards are eliminated (not just controlled) — this must be documented.
• Signage is required at permit spaces: "DANGER — PERMIT-REQUIRED CONFINED SPACE — DO NOT ENTER."

Atmospheric Testing Order

Always test in this sequence — never skip or reorder:

1. Oxygen content: must be 19.5%–23.5%
2. Flammability (LEL): must be <10% LEL before entry; <25% LEL during work
3. Toxic contaminants: CO, H₂S, and others — stay below applicable PELs/TLVs

Testing must be done with calibrated instruments. Test at top, middle, and bottom of space since gases stratify.

Roles in Confined Space Entry

Rescue Traps — The #1 Killer in Confined Spaces

• The most common confined space fatality scenario: an untrained would-be rescuer enters without PPE after a worker collapses and also succumbs.
• Non-entry rescue (tripod, lifeline, harness) must be attempted first when feasible.
• The attendant must not enter the space to perform rescue — call emergency services and use retrieval equipment.
• A new permit must be issued if the nature of the work or hazard changes — not just amended.
• Ventilation does not automatically make a permit space safe — it must be continuously monitored and conditions verified.