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Permit Required Confined Spaces

Quick Tips #115



On April 15, 1993, OSHA's permit-required confined spaces final rule (29 CFR 1910.146) went into effect. On December 1, 1998 OSHA published revisions to this rule to provide for:

  • Enhanced employee participation in the employer's permit-required space program
  • Authorized representatives with the opportunity to observe any testing or monitoring of permit spaces
  • Strengthening and clarifying the criteria employers must satisfy when preparing for timely rescue of incapacitated permit space entrants

The revisions became effective February 1, 1999.

OSHA defines a confined space as one that has limited or restricted means of entry or exit, is large enough for employees to enter and perform their work and is not designed for continuous occupancy (29 CFR 1910.146(b)). A permit-required confined space is a space that has one or more of the following characteristics:

  • Contains or could contain a hazardous atmosphere
  • Contains material that has the potential for engulfing the entrant
  • Inwardly converging walls
  • Any other recognized safety or health hazards

OSHA also specifies the requirements of a non-permit required confined space. This is a space that does not contain, or with respect to atmospheric hazards, have the potential to contain any hazard capable of causing death or serious physical harm.

There are several steps an employer should follow when beginning a confined space program. The first is to evaluate the workplace and determine whether it contains permit-required confined spaces as defined by OSHA. If it is determined that there are permit-required confined spaces, the employer must inform all exposed employees of the dangers by posting signs or some other equally effective means. Signs should read:


The next decision the employer must make is whether or not the confined space should be entered.

If NO–The employer must take effective measures to prevent employees from entering the permit space.

If YES–The employer must develop and implement a written permit space entry program.

This program must do the following:

  • Identify and evaluate permit space hazards before entry
  • Establish and implement means to prevent unauthorized entry
  • Establish and implement means to eliminate or control hazards necessary for safe entry by:
    • Specifying acceptable entry conditions
    • Isolating the space
    • Purging, inerting, flushing or continuously ventilating the permit space as necessary to eliminate or control atmospheric hazards
  • Provide, maintain and require the use of personal protective equipment necessary for safe entry
  • Require testing of atmospheric conditions inside the space before entry. Tests must be conducted for:
    • O2 (Oxygen, 19.5%–23.5% acceptable)
    • LEL (Lower Explosive Limit, <10% acceptable)
    • Toxins that may be present
  • Ensure that at least one attendant is stationed outside during entry
  • Coordinate with any contractors that are used
  • Implement rescue procedures
  • Establish the permit system, in writing
  • Review the permit system annually

OSHA also requires training to ensure that employees involved in confined space work can perform their job functions safely. This training covers specific items for the authorized entrant, the attendant and the entry supervisor. Training covers the following:

  • Authorized Entrant Responsibilities
    • Know the hazards involved in confined space entry
    • Select the appropriate personal protective equipment for confined space entry
    • Maintain communication with the attendant
    • Leave the space immediately when ordered by the attendant
    • Alert the attendant immediately if a problem develops
  • Attendant Duties
    • Remain outside unless relieved
    • Perform non-entry rescue when specified in procedure
    • Know existing and potential hazards of the confined space
    • Maintain communication at all times with entrants
    • Order evacuation of the space when conditions warrant
    • Summon rescue personnel when needed
    • Ensure unauthorized people stay clear of area
    • Perform no other duties that may interfere with attendant duties
  • Entry Supervisor Responsibility
    • Know the hazards involved with confined space entry
    • Know the company's permit system to remain consistent
    • Complete emergency planning

When an employer has designated a rescue and emergency service to perform confined space rescue, the employer is responsible for:

  • Evaluating a prospective rescuer's ability to respond to a rescue summons in a timely manner, considering the hazards identified (i.e. what is considered timely will vary according to the specific hazards involved in each entry)
  • Evaluating a prospective rescue service's ability, in terms of proficiency with rescue-related tasks and equipment, to function appropriately while rescuing entrants from the particular permit confined space or types of permit confined spaces that have been identified
  • Selecting a rescue team or service from those evaluated that has the capability to reach the victims within a time frame that is appropriate for the hazard identified and is equipped for and proficient in performing the needed rescue services
  • Informing each rescue team of the hazards they may confront when called to perform rescue at the site
  • Providing the rescue team or service selected with access to all permit spaces from which rescue may be necessary so that the rescue service can develop appropriate rescue plans and practice rescue operations

NOTE: Non-mandatory Appendix F -- Rescue team or rescue service evaluation criteria has been added to the 1910.146 to assist employers in their evaluation of rescue and emergency services.

Employers whose employees will perform rescue duties in confined spaces are responsible for:

  • Providing affected employees with the personal protective equipment (PPE) needed to conduct permit space rescues safely and the training of affected employees so they are proficient in the use of that PPE (PPE must be provided to the employee at no cost to them)
  • Training affected employees to perform assigned rescue duties. The employer must ensure that such employees successfully complete the training required to establish proficiency as an authorized entrant as required by 1910.146(g) and (h)
  • Training of affected employees in basic first aid and cardiopulmonary resuscitation (CPR). the employer must ensure that at least one member of the rescue team or service holding a current certification in first aid and CPR is available
  • Ensuring that affected employees practice making permit space rescues at least once every 12 months, by means of simulated rescue operations in which they remove dummies, manikins or actual persons from the actual representative permit confined spaces or permit spaces. Representative permit confined spaces must, with respect to opening size, configuration and accessibility, simulate the types of permit confined spaces from which rescue is to be performed


To facilitate non-entry rescue, retrieval systems or methods shall be used whenever an authorized entrant enters a permit space, unless the retrieval equipment would increase the overall risk of entry or would not contribute to the rescue of the entrant (29 CFR 1910.146(k)(3)).

Each authorized entrant shall use a chest or full body harness with a retrieval line attached at the center of the entrant's back near shoulder level, above the entrant's head, or at another point which the employer can establish presents a profile small enough for the successful removal of the entrant. Wristlets may be used in lieu of the chest or full body harness if the employer can demonstrate that the use of a chest or full body harness is infeasible or creates a greater hazard and that the use of wristlets is the safest and most effective alternative.

The other end of the retrieval line shall be attached to a mechanical device or fixed point outside the space so the rescue can begin as soon as the rescuer becomes aware that rescue is necessary. If the space is vertical and more than 5' deep, a mechanical device for removing the entrant must be available for use (29 CFR 1910.146(k)(3)(ii)).

The 1998 revision to the confined space standard gives employees and their authorized representatives the right to:

  • Participate in the development and implementation of all aspects of the permit space program required by 1910.146;
  • Review all supporting and determination data required under 1910.146
  • Observe pre-entry testing of the internal atmosphere and any periodic testing that is required
  • Review the certification that the space is safe to enter and that all pre-entry measures have been taken
  • Review the employer documentation that all hazards in a permit space have been eliminated
  • Request reevaluation of a permit space if the employee believes that the evaluation of that space may not have been adequate
  • Review immediately the results of any testing conducted in accordance with this standard
  • Review the completed permit

Employers should obtain a copy of 29 CFR 1910.146 to ensure that they are in full compliance with the standard. There are also several Appendices to the standard that provide information and non-mandatory guidelines to assist employers and employees in meeting the appropriate requirements.

Commonly Asked Questions
Q.   What air monitoring needs to be performed prior to entering a confined space?
A.   Air monitoring should be performed prior to entry. At a minimum, oxygen and LEL levels need to be monitored. If other toxins are suspected, then those levels also need to be monitored. Air should be monitored in the following order:
  1. Oxygen—Test for oxygen first in order to be sure you get an accurate LEL reading. Most combustible gas meters are oxygen-dependent and will not provide reliable readings in an oxygen-deficient atmosphere. Oxygen levels should be between 19.5 and 23.5%.
  2. LEL—Test flammable gas and vapor levels due to the threat of fire or explosion, which can be immediate and life threatening.
  3. Toxic air contaminants—Test for impurities such as carbon monoxide (CO), hydrogen sulfide (H2S) and chlorine (Cl2).
Q.   What is the difference between a two-way and a three-way confined space retrieval winch?
A.   The two-way winch is used for hoisting people and/or equipment into or out of the confined space. A three-way winch, which has a breaking mechanism, is used for fall protection. The only time a three-way winch should be used to hoist someone is if a fall has occurred and a rescue needs to be performed. Otherwise, the two-way winch should be used so the teeth on the three-way winch do not become worn and nonfunctional should a rescue need to be performed.
Q.   If I use my three-way winch for an emergency hoisting event, do I need to remove it from service and have it inspected?
A.   After an impact, the winch must be removed from service and inspected. Servicing may be required.
Q.   What is an immediately dangerous to life and health (IDLH) atmosphere?
A.   It is an atmospheric concentration of any toxic, corrosive or asphyxiant substance that poses an immediate threat to life or would cause irreversible or delayed adverse health effects or that would interfere with an individuals ability to escape unaided from a permit space.
Q.   Can an ambient air pump be used for confined space respiratory protection?
A.   Confined spaces may be immediately dangerous to life and health (IDLH). An IDLH environment requires an SCBA or an airline respirator with an escape bottle. Escape bottles are used in a high-pressure, pressure-demand format. An AABA (ambient air breathing apparatus) is a low-pressure, constant-flow product. Therefore, the high-pressure escape bottle and the low-pressure AABA will not work together.
Q.   If I monitor prior to entry and my readings are OK, do I need to continue monitoring while I'm in the confined space?
A.   Title 29 of the Code of Federal Regulations 1910.146 paragraph (c)(5)(ii)(F) requires periodic testing as necessary to ensure the space is maintained within the limits of the acceptable entry conditions. This is critical. OSHA states that all permit space atmospheres are dynamic due to variables such as temperature, pressure, physical characteristics of the material posing the atmospheric hazard, variable efficiency of ventilation equipment and air delivery system, etc.

The employer must determine and document on an individual permit space basis what the frequency of testing is and under what conditions the verification testing is done.

OSHA Confined Space Standard, 29 CFR 1910.146

(Rev. 12/2013)

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Please Note:
The content in this newsletter is intended for general information purposes only. This publication is not a substitute for review of the applicable government regulations and standards, and should not be construed as legal advice or opinion. Readers with specific compliance questions should refer to the cited regulation or consult with an attorney.

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