Permit-Required Confined Space Posting Under OSHA 1910.146

The one OSHA standard where a sign is not a best practice. It is the rule.

Most safety signage is a control you choose. Confined space signage is different: 29 CFR 1910.146(c)(2) requires employers to inform exposed employees of the existence, location, and danger of permit-required confined spaces by posting danger signs or by another equally effective means. The standard offers example wording: DANGER, PERMIT-REQUIRED CONFINED SPACE, DO NOT ENTER.

That makes this the category where an unposted space is itself a citation, before anyone goes in.

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What makes a space confined, and what makes it a permit space

A confined space meets all three: large enough for a person to enter and work, limited or restricted means of entry or exit, and not designed for continuous occupancy. Manholes, vaults, lift stations, tanks, silos, pits, digesters, and culverts all qualify.

A permit-required confined space is a confined space with at least one of the following:

• A hazardous atmosphere, or the potential for one
• Material that could engulf an entrant, such as grain, sand, or liquid
• An internal configuration that could trap or asphyxiate, such as inwardly converging walls or a sloping floor that tapers to a smaller cross-section
• Any other recognized serious safety or health hazard

The permit space is the one that must be posted, controlled by a written program, and entered only under a permit with an attendant outside.

What an entry looks like

The atmospheric numbers

• Oxygen: 19.5 to 23.5 percent. Below 19.5 is oxygen deficient. Above 23.5 is oxygen enriched, which turns ordinary materials into fuel
• Flammable gas or vapor: below 10 percent of the lower flammable limit
• Toxic gases: below the permissible exposure limit for each. Hydrogen sulfide and carbon monoxide are the common ones in sewers, vaults, and pits

Test in that order, oxygen first, because combustible and toxic sensors depend on oxygen to read correctly. Test at multiple depths, since gases stratify, and monitor continuously during entry rather than once at the start.

The roles

Entrant goes in, on a retrieval line where feasible. Attendant stays outside for the entire entry, maintains contact, monitors conditions, and orders evacuation. Entry supervisor authorizes the permit, verifies conditions, and terminates the entry. The attendant does not enter, ever, for any reason, including rescue.

The rescue problem

NIOSH investigations of confined space incidents have repeatedly found that in multiple-fatality events, most of the dead were would-be rescuers. Someone goes down. A coworker goes in after them without testing, without a line, without air. Then there are two.

This is why the standard prefers non-entry rescue, meaning a retrieval system that pulls the entrant out from above, and why the attendant is forbidden from entering. It is also the single most important thing a sign at the hatch can say to the person who did not attend the training.

Where signage fits

For once, the answer is simple. The standard requires it. Post every permit space at every point of entry: manhole lids, vault hatches, tank manways, silo access, lift station covers. The sign identifies the space as permit-required, prohibits entry, and does its most important work on the day someone who is not on the entry team is standing at the hatch deciding what to do.

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Sources: 29 CFR 1910.146, Permit-required confined spaces, including (c)(2) posting requirement and (d) permit-required confined space program; 29 CFR 1926 Subpart AA for construction; NIOSH confined space fatality investigations. Atmospheric limits are those defined in 1910.146(b).