Confined Space Safety
A confined space — a tank, vault, manhole, or deep trench — can be deadly, often from the air, not a fall.
Permit-required spaces
Many confined spaces are permit-required because of atmospheric or other hazards.
Before and during entry
- Test the atmosphere (oxygen, flammable gases, toxics) before and throughout entry.
- Ventilate the space.
- Post an attendant outside and have a rescue plan.
- Never enter to rescue without proper training and equipment — most confined-space deaths are would-be rescuers.
- Follow the entry permit procedure.
Going Deeper (Intermediate)
A confined space is large enough to enter, has limited entry/exit, and isn't designed for continuous occupancy (tanks, manholes, vaults, pits). It becomes a Permit-Required Confined Space (PRCS) if it has a hazardous atmosphere, engulfment risk, entrapment configuration, or any other serious hazard. Construction's standard is Subpart AA (1926.1200).
Most confined-space deaths are would-be rescuers who rush in — never enter to save someone without the system in place.
Advanced / Pro-Level
The PRCS entry system:
- Atmospheric testing before and during entry, in order: oxygen (19.5–23.5%), then flammables (<10% LEL), then toxics (e.g., H₂S, CO) — with a calibrated/bump-tested meter.
- Roles: trained entrant, attendant (stays outside, maintains contact, never enters), and entry supervisor who signs the permit.
- Continuous ventilation, non-sparking tools/lighting where flammables exist, and retrieval equipment (harness + tripod/winch) for non-entry rescue.
- LOTO any mechanical/flow hazards (don't get buried by product flowing in).
- A written rescue plan with a capable rescue service on call — not "we'll call 911."
Practice Challenge
A meter reads O₂ 20.9%, LEL 0%, H₂S 0 ppm before entry, but there's a possibility of decaying organics. What two ongoing controls are essential during entry? (Answer: continuous atmospheric monitoring (conditions change) and continuous mechanical ventilation, with an attendant and retrieval gear staged for non-entry rescue.)
In Practice
A worker collapses in a tank; a coworker rushes in to help and collapses too — from the same bad air. That's why you never make an untrained rescue and always test the atmosphere first.
Common Mistakes to Avoid
- Entering without testing the atmosphere
- Making an untrained rescue (the #1 confined-space killer)
- Skipping the entry permit and attendant
Takeaway: Test and ventilate the air, post an attendant, follow the permit — and never make an untrained rescue; that's how rescuers die.
⚠️ Educational overview — NOT official OSHA certification. Get formal training from an authorized trainer and follow current OSHA standards (29 CFR 1926) and your employer's program.