The Definition of Permit-Required Confined Space

Definition of Permit-Required Confined Space

A permit-required confined space, or permit space, is a confined space that has one or more serious hazards. Under OSHA 29 CFR 1910.146, a confined space requires a permit if it contains or could contain a hazardous atmosphere, contains material that could engulf an entrant, has an internal shape that could trap or asphyxiate someone, such as inwardly sloping walls, or contains any other recognized serious safety or health hazard.

Entry into a permit space is controlled through a written permit program. Before entry, the employer must test the atmosphere, isolate hazards, assign trained entrants, an attendant and an entry supervisor, and arrange rescue. Construction work in confined spaces falls under a separate OSHA standard, 29 CFR 1926 Subpart AA.

Key Facts About Permit-Required Confined Spaces

• Atmospheres are tested in order: oxygen first, then flammable gases and vapors, then toxic contaminants.
• Acceptable oxygen levels are 19.5 to 23.5 percent; flammable gas must be below 10 percent of the LEL.
• Employers must post danger signs or otherwise inform workers of permit spaces.
• Rescue services must be able to respond in a timely manner for the hazards present.
• Many confined space deaths are would-be rescuers who enter without protection.

Example of a Permit-Required Confined Space

A food plant needs to clean the inside of a large mixing tank. Because the tank has agitator blades and residual cleaning chemicals, it is classified as a permit space. The crew locks out the agitator, ventilates the tank, tests the air, completes the entry permit and posts an attendant at the manway with a retrieval system in place.

How to Manage Permit-Required Confined Spaces

1. Survey the workplace and identify all confined spaces and permit spaces.
2. Post warnings and prevent unauthorized entry.
3. Write a permit program covering testing, isolation, ventilation, roles and rescue.
4. Train entrants, attendants and entry supervisors for their duties.
5. Issue a permit for each entry, monitor conditions and cancel the permit when work ends.

Related Terms

• Confined Space
• Attendant (Confined Space)
• Permit to Work
• Oxygen-Deficient Atmosphere
• Gas Detection

Frequently Asked Questions: Permit-Required Confined Space

What is the difference between a confined space and a permit-required confined space?

Every permit space is a confined space, but not every confined space needs a permit. A permit is required only when serious hazards such as a hazardous atmosphere, engulfment or entrapment are present or possible.

Can a permit space be reclassified as non-permit?

Yes. If all hazards are eliminated, not just controlled, and this is documented, OSHA allows a space to be reclassified for as long as the hazards remain eliminated.

Who can sign a confined space entry permit?

The entry supervisor signs the permit after verifying that tests are acceptable and all required procedures and equipment are in place.