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Confined Space Entry Procedures

The following sections cover proper procedures and guidelines for safely working within confined spaces.

Note: Electric manholes and other confined spaces with high voltage electrical hazards are covered by 29 CFR 1910.269. Please refer to the code for more information.

IMPORTANT: If you intend to perform hotwork within the confined space, you must note this on the form.

  • Before entering a confined space, evaluate the area and complete the Confined Space Checklist Form and Entry Document. A sample form addressing OSHA requirements is included after this section.

    To complete the form, determine the following information:

    • Identity and location of the confined space
    • Purpose for entering the area
    • Known and potential hazards
    • Required isolation methods (e.g., lockout/tagout)
    • Environmental conditions of the confined space
    • Atmospheric readings to verify that acceptable environmental conditions are met and maintained
    • Rescue services, procedures, and equipment that may be necessary in case of an emergency
    • Communication procedures to be used
    • Personal protective equipment to be used
    • Any additional information relating to the specific circumstances of the confined space
    • Names of the following: Person authorizing entry
      • Supervisor
      • Authorized entrants
      • Authorized attendants

    If you intend to perform hotwork within the confined space, you must note this on the form.

  • Employees must notify the person who authorizes entry before working in confined spaces.

    The person who authorizes entry refers to any records on file and identifies the actual or potential hazards of the area in question. If no file exists for the specific space, a new one is developed.

    The person who authorizes entry then reviews and approves the entry form as appropriate. A copy of the form is filed for future reference.

  • Before entering a confined space, all employees involved with the entry must attend a preparation meeting. The agenda for this meeting includes the following:

    • Discussion of actual and potential hazards
    • Review of emergency procedures including rescue and evacuation
    • Completion of the entry form by all team members to acknowledge their understanding of the hazards involved with the confined space
    • Issuance of personal protective equipment
    • Discussion of site location and other essential information
  • Overview

    Due to poor ventilation and physical structure, the atmosphere in confined spaces may be actually or potentially hazardous. Atmospheric hazards include the following:

    • Oxygen deficient or oxygen enriched atmospheres
    • Combustible atmospheres
    • Toxic atmospheres
    • Any other atmosphere that is immediately dangerous to life or health

    Employees trained in atmospheric monitoring will test several points in a confined space for the following:

    • Oxygen content
    • Combustible atmosphere
    • Potential toxic contaminants

    Oxygen Atmospheres

    Oxygen enriched atmospheres are more than 23.5% oxygen; oxygen deficient atmospheres are less than 19.5% oxygen. Certain chemical or biological reactions may reduce oxygen over time, but employee operations such as cutting or welding may reduce oxygen content very quickly. Oxygen levels must be tested regularly whenever hotwork is performed within a confined space. The following graph outlines human reaction to various oxygen levels.


    Oxygen Concentrations

    Figure: Human reaction to oxygen concentrations

    Combustible Atmospheres

    Combustible atmospheres have enough oxygen and flammable vapor, gas, or dust to ignite and support a fire or explosion if exposed to flames, sparks, or heat. Oxygen-enriched atmospheres and hazardous atmospheres in excess of their lower flammable limits are extremely combustible and dangerous. The following graphic illustrated the relationship between oxygen, heat, and fuel.

    Figure: Combustible atmospheres

    Toxic Atmospheres

    Toxic atmospheres can cause injury, illness, or death. Safety concerns include inhalation and skin exposure. If the identity of the toxic atmosphere is known, check all appropriate Material Safety Data Sheets (MSDSs) for threshold limit values and recommended personal protective equipment. If the identity of the toxic atmosphere is not known, use maximum PPE (i.e. SCBA).


  • Ventilation controls the atmospheric hazards of a confined space by replacing unsafe air with clean, breathable air. There are several methods for ventilating a confined space. The method and equipment used depend on the following factors:

    • Size of the confined space
    • Atmosphere
    • Source of the makeup air

    For most confined spaces, fans or other air-moving equipment can provide adequate ventilation. Two common types of mechanical ventilation include local exhaust ventilation and general ventilation.

    Local exhaust ventilation captures contaminants at their point of origin and removes them. This type of ventilation method is ideal for flammable and toxic materials produced at a single point (e.g., hotwork and work involving cleaning solvents). When using this type of ventilation system, keep the exhaust intake close to your work. Do not use this type of ventilation system for contaminants that are widely dispersed or for confined spaces that make ventilation difficult. Instead, use general ventilation.

    General ventilation flushes the atmosphere by supplying and exhausting large volumes of air. Because this system does not reduce the amount of contaminants released, it is not recommended for highly toxic atmospheres. General ventilation is ideal for providing oxygen and controlling low concentrations of materials that are not highly toxic. When using this type of ventilation system during hotwork, monitor the atmosphere continuously and wear a SCBA, as necessary.

    Ventilation alone cannot reduce some atmospheric hazards to safe levels. Use atmospheric testing to confirm whether the ventilation system has been successful.

    Follow these guidelines for ventilating confined spaces:

    • Begin ventilation in time to assure that the space is safe before entry.
    • Test the atmosphere before entry to confirm that the ventilation system is working properly and that the space is safe.
    • Continue ventilation as long as the space is occupied, or at least until the oxygen levels and hazardous concentrations are within safe limits.
    • If work inside the space can make the air unsafe (e.g., hotwork, painting, using solvents, sandblasting, etc.) continue ventilating.

    Ventilation System Example

    Figure: Ventilation system example

  • Employees must complete the following steps to prepare confined spaces for entry:

    • Isolate the confined space entry site from the surrounding area using guards and barriers (including signs, rope, or tape).
    • Drain, clean, ventilate, and/or purge the confined space, as necessary, to prevent flammable, toxic, and corrosive hazards.
    • Isolate all electrical, mechanical, and pneumatic energy sources as outlined in the Lockout/Tagout section of this manual.
    • Ensure that all workers are wearing appropriate personal protective equipment, and that all persons wearing respirators have been properly trained in their usage.
    • Provide continuous ventilation, as necessary.
    • Ensure that non-sparking tools and explosion proof equipment are used when working in a potentially combustible atmosphere.
    • Position gas cylinders for cutting or burning outside the confined space.
    • Ensure that a standby SCBA is available.
    • Obtain personal protective equipment, including lifelines, winches, and harnesses, as required. Ensure that the equipment has been inspected as scheduled.
    • Take precautions to ensure against engulfment hazards, such as water, dirt, grain, etc.
  • Life support safety is critical during confined space operations. The following items are requirements for safeguarding confined spaces:

    • Employees must wear appropriate personal protective equipment at all times.
    • Employees must use harnesses, lifelines, and/or winches, as appropriate.

    The Authorized Safety Attendant is specifically responsible for the following:

    • Keeping a log of all authorized entrants working within the confined space
    • Maintaining constant verbal contact with the authorized entrants within a confined space
    • Taking necessary precautions and measures to prevent unauthorized persons from entering a confined space
    • Initiating evacuation procedures whenever conditions within or outside the confined space pose a new hazard

    All employees must evacuate a confined space when one or more of the following conditions occur:

    • Authorized Safety Attendant orders evacuation
    • Automatic atmospheric alarm sounds
    • Authorized entrants believe they are in danger
  • If a worker is unable to evacuate the confined space during an emergency, the Authorized Safety Attendant will contact rescue personnel by radio or other means.

    The Authorized Safety Attendant and other workers outside the confined space should attempt to hoist the worker out of the confined space using a lifeline.

    Under no circumstances should unauthorized employees enter a confined space during an emergency.