Plant-Wide Hazards » Confined Spaces

Specific OSHA Requirements

The user of this adviser is encouraged to consult the standard and other documents referenced below for additional information.

29 CFR 1910 Subpart J, Occupational safety and health standards

  • 1910.146, Permit-required confined spaces

Permit-Required Confined Spaces (PDF). OSHA Publication 3138, (2004).

Small Business Handbook. OSHA Publication 2209, (2024) [Español OSHA Publication 4261, (2024)].

Application of the Permit-Required Confined Spaces (PRCS) Standards, 29 CFR 1910.146. OSHA Directive CPL 02-00-100 [CPL 2.100], (May 5, 1995).

NOTE: Employers in states with state-run safety and health plans should check with their state agency. Their state may enforce standards that, while "as effective as federal standards," may not be identical to the federal requirements.

What is a confined space?

A confined space has limited or restricted means of entry or exit, is large enough for an employee to enter and perform assigned work, and is not designed for continuous occupancy by the employee.

Examples of confined spaces are:

  • Underground vaults,
  • Tanks,
  • Storage bins,
  • Pits and diked areas,
  • Vessels, and
  • Silos.
What are the hazards that may be associated with confined spaces?

Because of the difficulties of entry and exit from confined spaces, employees who work in them may also face increased risk of exposure to serious injury from hazards such as entrapment, engulfment, and hazardous atmospheric conditions.

The atmosphere in a confined space can be hazardous due to the presence of chemicals that are either man-made, such as toxic fumes from welding operations, or naturally occurring, such as hydrogen sulfide or methane that can result from decomposing organic material. The oxygen level in a confined space may be reduced below that required for normal breathing. Gases that are heavier than air, such as carbon dioxide, may sink to the bottom of a confined space and reduce the level of oxygen breathed by a worker. Or chemical processes such as the formation of rust or bacterial action, as in the fermentation process, can use up the oxygen in a confined space.

In addition, the presence of flammable liquids or gases in a confined space presents a fire or explosion hazard

Work in confined spaces may keep employees closer to machinery components and power-driven equipment, such as augers, than they would be otherwise.

Heat, noise, vibration, and structural hazards such as scaffolding installed for maintenance, overhead structural members, or baffles also contribute to potentially unsafe conditions in confined spaces.

How does OSHA regulate confined spaces?

OSHA regulates confined spaces that have one or more of the following characteristics:

  1. contains or has the potential to contain a hazardous atmosphere;
  2. contains a material that has the potential for engulfing an entrant;
  3. has an internal configuration that might cause an entrant to be trapped or asphyxiated by inwardly converging walls or by a floor that slopes downward and tapers to a smaller cross section; and/or
  4. contains any other recognized serious safety or health hazards.

Such confined spaces are defined as "permit-required confined spaces" or "permit spaces" and are regulated by OSHA's standard 29 CFR 1910.146. See Confined Space vs. Permit-Required Confined Space.

Confined Space Case

The tank was located on the second floor and was part of a chicken processing operation at a rendering plant. The inside of the tank measured 8 feet high by 6-1/2 feet in diameter. The bottom of the tank was cone-shaped and sloped outward at a 120-degree angle. The to of the tank was covered with loose plate steel, one-third of which had been removed just prior to employee's entry. Employee was to enter the tank to repair a hole in the bottom. The only witnesses to this operation were two other employees who observed from outside the tank. Upon entering the tank, the employee was immediately overcome by a gaseous, oxygen-deficient atmosphere. When he tried to climb out, he fell backward into the tank and apparently lost consciousness. Local authorities were unable to revive him. The gas present in the tank was identified as methane.

  • Confined Space
    • Limited or restricted means of entry or exit.
    • Large enough for an employee to enter and perform assigned work.
    • Not designed for continuous occupancy.
  • Permit-required confined space
    • Meets definition of a confined space, and
    • Has one or more of the following
      • Contains of has potential to contain a hazardous atmosphere,
      • Contains a material that has the potential for engulfing an entrant,
      • Has internal configuration that might cause an entrant to be trapped or asphyxiated, and
      • Contains any other recognized safety or health hazards.
  • Evaluate workplace for permit-required confined spaces.
  • Inform exposed employees of
    • Existence of permit spaces,
    • location, and
    • danger posed by the spaces.
  • Take measures to prevent unauthorized entry into permit spaces.
  • Develop written program.
  • Permits
    • Are signed by entry supervisor;
    • verify that pre-entry preparations completed and space safe to enter;
    • are posted at entrances or otherwise made available to entrants;
    • do not exceed time required to complete assignment;
    • are canceled when assignment complete or new conditions exist; and
    • are kept for at least 1 year
  • Test results: oxygen, flammable, toxic contaminants
  • Tester's initials or signature
  • Name and signature of supervisor who authorizes entry
  • Name of permit space to be entered, authorized entrant(s), eligible attendants, and individual(s) authorized to be entry supervisor(s)
  • Purpose of entry and known space hazards
  • Measures to be taken to isolate permit spaces and to eliminate or control space hazards
  • Name and telephone numbers of rescue and emergency services
  • Date and authorized duration of entry
  • Acceptable entry conditions
  • Communication procedures and equipment to maintain contact during entry
  • Additional permit(s), such as for hot work, that have been issued to authorize work in the permit space
  • Special equipment and procedures, including personal protective equipment and alarm systems
  • Any other information needed to ensure employee safety
  • Contractors must be informed of
    • Permit spaces and entry requirements,
    • identified hazards,
    • employer's experience with the space,
    • precautions or procedures to be followed when in or near permit spaces,
    • multiple employers must coordinate entry operations, and
    • contractors must be debriefed at the conclusion of entry operations.
Where are "permit-required confined spaces" found in the poultry processing industry?

The following are examples of areas in poultry processing that need to be evaluated to see if they meet the definition of a "permit-required confined space" (View examples):

  • Ice houses;
  • Packing area: blast freezers chilled by carbon dioxide or nitrogen;
  • Offal area: vats and pits;
  • Wastewater handling/treatment area: settling tanks or vats, tanks of sulfuric acid, hydroxides, or other chemicals; and
  • Gas storage areas: large ammonia, carbon dioxide, nitrogen, or chlorine tanks.

An actual case (see Confined Space Case) involved an employee who entered a tank that had contained chicken blood.

What are an employer's responsibilities with regard to permit-required confined spaces?

[Decision Flow Chart]

OSHA's standard requires employers to determine whether there are any permit-required confined spaces in their facility.

If there are, employees must be informed of them and of the dangers posed by them. See Confined Space Requirements.

If employees are not to enter and work in permit spaces, the employer must take effective steps to prevent employee entry.

If employees are to enter permit spaces, the employer must develop a written permit space program, which will (see Permit System and Entry Permit Requirements):

  • Identify and evaluate permit space hazards before allowing employee entry;
  • Test conditions in the permit space before entry operations and monitor the space during entry;
  • Perform, in the following sequence, appropriate testing for atmospheric hazards: oxygen, combustible gases or vapors, and toxic gases or vapors;
  • Implement necessary measures to prevent unauthorized entry;
  • Establish and implement the means, procedures and practices - such as specifying acceptable entry conditions, isolating the permit space, providing barriers, verifying acceptable entry conditions, purging, making inert, flushing, or ventilating the permit space - to eliminate or control hazards necessary for safe permit-space entry operations;
  • Identify employee job duties;
  • Provide, maintain, and require, at no cost to the employee, the use of personal protective equipment and any other equipment necessary for safe entry (e.g., testing, monitoring, ventilating, communicating, and lighting equipment; barriers, shields, and ladders);
  • Ensure that at least one attendant is stationed outside the permit space for the duration of entry operations;
  • Coordinate entry operations when employees of more than one employer are to be working in the permit space;
  • Implement appropriate procedures for summoning rescue and emergency services;
  • Establish, in writing, and implement a system for the preparation, issuance, use, and cancellation of entry permits;
  • Review established entry operations annually and revise the permit-space entry program as necessary; and
  • When an attendant is required to monitor multiple spaces, implement the procedures to be followed during an emergency in one or more of the permit spaces being monitored.

Before initial work assignments, employees must be trained in the understanding, knowledge, and skills necessary for the safe performance of their duties.

Additional training is required when:

  • Job duties change,
  • There is a change in the permit-space program or the permit space operation presents a new hazard, and
  • When an employee's job performance shows deficiencies.

Rescue team members must have also been trained in:

  • Proper use of personal protective equipment and rescue equipment,
  • Performance of assigned rescue duties,
  • First aid and cardiopulmonary resuscitation (CPR), and
  • Yearly practice rescue exercises.

The standard also requires coordination with contractors. See Multi-Employer Requirements.