Working In Permit-Required Confined Spaces

Mark Stromme, Contributor

Many workplaces contain areas that are considered “confined spaces.” These confined spaces are not necessarily designed for continuous occupancy by employees, but they are large enough for workers to enter and conduct inspections, perform minor repairs and perform maintenance activities.

Know the Difference

Confined spaces are different from permit-required confined spaces. A confined space is a space that:

  • Is large enough and so configured that an employee can bodily enter and perform assigned work
  • Has limited or restricted means for entry or exit (for example, tanks, vessels, silos, storage bins, hoppers, vaults and pits are spaces that may have limited means of entry)
  • Is not designed for continuous employee occupancy

A permit-required confined space (permit space) is a confined space that has one or more of the following characteristics:

  • Contains or has a potential to contain a hazardous atmosphere
  • Contains a material that has the potential for engulfing an entrant
  • Has an internal configuration, such that an entrant could be trapped or asphyxiated by inwardly converging walls or by a floor which slopes downward and tapers to a smaller cross-section
  • Contains any other recognized serious safety or health hazard, such as unguarded machinery, exposed live wires or heat stress

Workers who enter confined spaces can be exposed to multiple hazards, any of which may cause bodily injury, illness or death. Supervisors and workers required to enter confined spaces must:

  • Understand the nature of confined space hazards
  • Be able to recognize signs or symptoms of exposure
  • Understand the consequences of exposure to hazards

Understand the Hazards

Confined space hazards are categorized as physical or atmospheric. Physical hazards include:

  • Mechanical, electrical and hydraulic energy
  • Communication problems
  • Noise
  • Entry and exit difficulties
  • Activated electrical or mechanical equipment
  • Water entering the confined space
  • Underground utilities
  • Temperature extremes

Many of these hazards can be eliminated, or “locked-out,” before entry into a confined space.

Atmospheric hazards include oxygen deficiency, flammable air and toxic air contaminants. The largest number of confined space deaths are a result of atmospheric problems.

Oxygen deficient air—An oxygen-deficient atmosphere has less than 19.5% available oxygen. Oxygen levels in a confined space can decrease because of: (1) work being done, such as welding or cutting; (2) chemical reactions (rusting); (3) bacterial action (fermentation); and (4) displacement by another gas, such as sulfur dioxide. Any atmosphere with less than 19.5% oxygen must not be entered without an approved self-contained breathing apparatus.

Flammable atmospheres—Two things make an atmosphere flammable: (1) the oxygen in air; and (2) a flammable gas, vapor or dust in the proper mixture. Different gases have different flammable ranges. If a source of ignition (e.g., a sparking or electrical tool) is introduced into a space containing a flammable atmosphere, an explosion will result.

An oxygen-enriched atmosphere (above 23.5%) will cause flammable materials, such as clothing and hair, to burn violently when ignited. Never use pure oxygen to ventilate a confined space. Ventilate with normal air.

Toxic atmospheres—Most substances (liquids, vapors, gases, mists, solid materials and dusts) should be considered hazardous in a confined space. Toxic substances can come from products stored in the space; work being performed in the space (welding, painting, cleaning, etc.); or areas adjacent to the confined space.

Do a Hazard Assessment

Before entry into a confined space is allowed, hazard assessment and hazard control must be performed. A hazard assessment is looking for all known or potential hazards. One example of hazard assessment would be testing an atmosphere.

Hazard control is systematically addressing each hazard discovered in your assessment and either eliminating or controlling the hazard. Continuous ventilation of a confined space would be eliminating a hazard; locking out or tagging out a mechanical device would be controlling a hazard.

Evaluate the Workplace

Employers are required to evaluate the workplace to identify all permit-required confined spaces. The employer must inform employees of the confined spaces and their dangers; must post warning signs; and must take measures to prevent unauthorized employees from entering permit spaces.

If permit spaces exist, the employer must develop and implement a written permit space program. The written program must be available for inspection by employees and their authorized representatives.

The permit space program must:

  • Implement the measures necessary to prevent unauthorized entry
  • Identify and evaluate the hazards of permit spaces before employees enter them
  • Develop and implement the means, procedures, and practices necessary for safe permit space entry operations
  • Provide protective equipment
  • Explain the duties of the authorized entrants
  • Have provisions for informing contract workers of the presence of permit-required confined spaces

Train Employees

Employers must provide training to employees so that they acquire the understanding, knowledge and skills necessary for the safe performance of duties.

Employees must be trained when:

  • First assigned to duties in and around permit spaces
  • Before there is a change in assigned duties
  • Whenever there is a change in operations that presents a hazard
  • Whenever the permit-space entry procedures change

Make sure certification of this training is available for inspection by employees or their authorized representatives.


Employers must describe the potential hazards that employees at the worksites might encounter and instruct them as to how they might recognize these hazards. Review your workplace confined space program, along with how air monitoring devices work. IHW

About the Author:

Mark Stromme joined JJ Keller & Associates, Inc. in 1994. With a background in monitoring OSHA, EPA and DOT regulations, he specializes in the OSHA 1926 construction and 1910 general industry regulations. His focus is on oil & gas safety, construction safety, electrical safety, mobile cranes, scaffolding, excavations & fall protection. An authorized OSHA Construction Outreach Trainer, Stromme is responsible for monitoring, analyzing and summarizing 1910 and 1926 regulations for various J. J. Keller guides, manuals and newsletters. ( and

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