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Confined Spaces in Construction



OSHA's 1926 Subpart AA, Confined Spaces in Construction, standard applies to construction work performed in confined spaces, except for certain construction activities that are subject to confined space provisions in other OSHA construction standards.

The activities excluded from this standard are:

  • Diving – regulated by 29 CFR Part 1926 subpart Y.
  • Excavations – regulated by 29 CFR Part 1926 subpart P.
  • Underground Construction, Caissons, Cofferdams and Compressed Air – regulated by 29 CFR Part 1926 subpart S.

Before work begins at a worksite, each employer must ensure that a competent person:

  • identifies all confined spaces in which one or more of the employees it directs may work, and
  • identifies each space that is a permit space, through consideration and evaluation of the elements of that space, including testing as necessary.

Click on the button to see confined spaces that can be found on construction site.

Confined spaces that may be found on construction sites:

Confined spaces that may be found on construction sites include, but are not limited to:

  • Maintenance hole (such as sewer, storm drain, electrical, communication, or other utility)
  • Sewers
  • Storm drains
  • Water mains
  • Lift stations
  • Tanks (such as fuel, chemical, water or other liquid, solid or gas)
  • Pits (such as elevator, escalator pump, valve or other equipment)
  • Bins
  • Boilers
  • Incinerators
  • Scrubbers
  • Concrete pier columns
  • Transformer vaults
  • Heating, ventilation, and air conditioning (HVAC) ducts
  • Precast concrete and other pre-formed manhole units
  • Drilled shafts
  • Enclosed beams
  • Vessels
  • Digesters
  • Cesspools
  • Silos
  • Air receivers
  • Sludge gates
  • Air preheaters
  • Transformers
  • Turbines
  • Chillers
  • Bag houses
  • Mixers/reactors
  • Crawl spaces
  • Attics
  • Basements (before steps are installed).
  • 1. Before work begins at a worksite, each employer must ensure that a competent person identifies _____.

    a. all non-permit spaces and permit spaces
    b. only potential permit spaces
    c. possible sewer systems
    d. underground facilities

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    The Confined Space Standard


    OSHA's standard, 29 CFR 1926 Subpart AA, Confined Spaces in Construction, sets forth requirements to protect employees on construction worksites with confined spaces. Let's look at a summary of OSHA 1926.1203, General requirements.

    Per OSHA 1926.1203(b), if the workplace contains one or more permit spaces, the employer who identifies, or who receives notice of, a permit space must:

    • Inform exposed employees by posting danger signs or by any other means, of the existence, location, and dangers posed by each permit space; and
    • Inform, in a manner other than posting, authorized employee representatives and controlling contractors about each permit space.

    If employees will enter a permit space, the employer must have a written permit space program per OSHA 1926.1204 at the construction site. The written program must be made available prior to and during entry operations for inspection by employees and their authorized representatives.

    An employer may use the alternate procedures for entering a permit space only under the conditions set forth in OSHA 1926.1203(e)(1).

    When there are changes in a non-permit confined space that might increase the hazards or some indicate that the initial evaluation of the space may not have been adequate, a competent person must reevaluate that space and, if necessary, reclassify it as a permit-required confined space per OSHA 1926.1203(g) requirements.

    A permit-required confined space may only be reclassified as a non-permit confined space by a competent person determines that all OSHA 1926.1203(g) requirements have been met.

    Before entry operations begin, the host employer must provide confined space location, previous entry, and hazard information, if it has it, to the controlling contractor OSHA 1926.1203(h) requirements.

    If there is no controlling contractor at the worksite, the host employer or other employer who arranges to have employees perform permit space entry, will perform that role per OSHA 1926.1203(i).

    2. If employees will enter a permit space on a construction worksite, the employer must _____.

    a. have a written permit space program
    b. isolate permit spaces
    c. require permits for all spaces
    d. report all confined space entries to OSHA

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    Construction Employer Classifications

    The host employer owns or manages the property on which construction is taking place.

    The controlling contractor is the employer that has overall responsibility for construction at the worksite.

    If a host employer has overall responsibility for construction at the worksite, then they are both a host employer and a controlling contractor.

    The subcontractor is the junior or secondary contractor who contracts with the controlling or "prime" contractor to perform some or all contractual-obligations under the prime contract.

    The entry employer is usually a subcontractor who directs workers to enter a confined space for work or rescue.

    Information flow and coordination among employers.
    (Click to enlarge)

    Coordinating Confined Space Entry

    The rule makes the controlling contractor, rather than the host employer, the primary point of contact for information about permit spaces at the worksite. The host employer must provide information about permit spaces at the worksite to the controlling contractor, who then passes it on to the employers whose employees will enter the spaces (entry employers).

    Likewise, entry employers must give the controlling contractor information about their entry program and the hazards they encounter in the space. The controlling contractor then passes that information on to other entry employers and back to the host. As mentioned above, the controlling contractor is also responsible for making sure employers outside a space know not to create hazards in the space, and that entry employers working in a space at the same time do not create hazards for one another’s workers.

    3. Who has overall responsibility for construction at the worksite?

    a. Worksite supervisor
    b. Controlling contractor
    c. Host employer
    d. Entry employer

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    Key Requirements

    There are five key requirements in the new construction rule, and several areas where OSHA has clarified existing requirements. The five new requirements include:

    1. There are more detailed provisions that require coordinated activities when there are multiple employers at the worksite. This requirement will ensure hazards are not introduced into a confined space by workers performing tasks outside the space. An example would be a generator running near the entrance of a confined space causing a buildup of carbon monoxide within the space.
    2. It requires a competent person to evaluate the work site and identify confined spaces, including permit spaces.
    3. It requires continuous atmospheric monitoring whenever possible.
    4. It requires continuous monitoring of engulfment hazards. For example, when workers perform work in a storm sewer, a storm upstream from the workers could cause flash flooding. An electronic sensor or observer posted upstream from the worksite could alert workers in the space at the first sign of the hazard, giving the workers time to evacuate the space safely.
    5. It allows for the suspension of a permit, instead of cancellation, in the event of changes from the entry conditions list on the permit or an unexpected event requiring evacuation of the space. The space must be returned to the entry conditions listed on the permit before re-entry.

    In addition, OSHA has added provisions to the construction rule that clarifies existing requirements in the General Industry standard. These include:

    1. Requiring that employers who direct workers to enter a space without using a complete permit system prevent workers’ exposure to physical hazards by eliminating the hazard or through isolation methods such as lockout/tagout.
    2. Requiring that employers who are relying on local emergency services for emergency services arrange for responders to give the employer advance notice if they will be unable to respond for a period of time (because they are responding to another emergency, attending department-wide training, etc.).
    3. Requiring employers to provide training in a language and vocabulary that the worker understands.

    4. Why is continuous monitoring of engulfment hazards required when workers are in a storm sewer?

    a. To alert workers of a flash flood
    b. To make sure workers are not asphyxiated
    c. So workers can identify biological hazards
    d. To prevent engulfment by weak soil

    Next Section

    Crawl Spaces and Attics

    crawl spaces

    Crawl spaces and attics can be both confined spaces and permit-required confined spaces under the new standard. For instance, working in an attic and applying a large amount of spray foam (or another chemical) in a short period of time can expose a worker to low oxygen levels or a hazardous atmosphere.

    Also, changes to the entry/exit, the ease of exit, and airflow could create a confined space or cause the space to become permit-required.

    Hazards in Crawl Spaces and Attics

    Crawl spaces can present many confined space hazards, including:

    • Atmospheric hazards (e.g., flammable vapors, low oxygen levels)
    • Electrocution (e.g., using electrical equipment in wet conditions, unprotected energized wires)
    • Standing water
    • Poor lighting
    • Structural collapse
    • Asbestos insulation
    • Heat stress/cold stress

    Working in attics can present confined space hazards, such as:

    • Atmospheric hazards (e.g., poor ventilation)
    • Heat stress/cold stress
    • Mechanical hazards (e.g., attic ventilators, whole house fans)
    • Electrical hazards (e.g., damaged or frayed wires, open electrical boxes)
    • Slip, trip and fall hazards
    • Asbestos insulation

    5. Which of the following hazards is typically found in crawl spaces?

    a. Mechanical hazards
    b. Excessive noise
    c. Fall hazards
    d. Standing water

    Next Section

    Confined Spaces in Pits


    Even though a pit is typically open on top and over 4 feet deep, it can still be a confined space or permit-required confined space, most commonly due to exposure to hazardous atmospheres.

    Pits can be completely underground or below grade, such as a utility vault within a sewer system or a pit within a pit in a wastewater treatment plant.

    Pits are found in many environments. Examples include:

    • sump pits
    • valve pits or vaults (e.g., wastewater treatment plants, municipal water systems)
    • electrical pits/vaults
    • steam pits/vaults
    • vehicle service/garage pits
    • elevator pits
    • dock leveler pits
    • industrial chemical waste pits

    Many of these spaces qualify as permit-required confined spaces.

    Employers must take all necessary steps to keep workers safe in confined spaces, including following the OSHA Construction Confined Spaces standard. This standard applies to both new construction in a pit and alterations and/or upgrades. Among the pit-related tasks covered by the standard are:

    • opening or closing valves during renovation work
    • installing or upgrading pump equipment, cables, or junction boxes

    Construction work can create confined spaces, even if there are none at the start of a project. Changes to the entry/exit, the ease of exit, and airflow could produce a confined space or cause one to become permit-required.

    6. What is the most common confined space hazard in pits?

    a. Slips and trips
    b. Impact hazards
    c. Hazardous atmospheres
    d. Biological hazards

    Next Section

    Confined Spaces in Sewer Systems

    sewer systems

    Types of sewer systems include sanitary (domestic sewage), storm (runoff), and combined (domestic sewage and runoff). Sewer systems are extensive and have different components that are considered confined spaces, including pipelines, manholes, wet wells, dry well vaults, and lift/pump stations. Therefore, employers conducting work in sewer systems will likely have workers who will encounter confined spaces.

    Sewer systems also consist of wastewater treatment plants, where confined spaces include digestion and sedimentation tanks, floating covers over tanks, sodium hypochlorite tanks, and wastewater holding tanks, among others. Many of these components may also qualify as permit-required confined spaces.

    Hazards Associated with Sewer Systems

    Sewer systems can present a host of confined space hazards, including:

    • atmospheric hazards (low oxygen, toxic or flammable gases)
    • chemicals in piping and from roadway runoff (may harm lungs, skin, or eyes)
    • engulfment and drowning
    • electrocution (e.g., using electrical equipment in wet working conditions)
    • slips, trips, and falls
    • falling objects
    • high noise levels, low visibility, limits to communication, and long distances to exits

    For more information about hazards in the construction industry, read OSHA’s Anatomy of Confined Spaces in Construction.

    For a complete discussion of confined space safety, be sure to take OSHAcademy Course 713, Confined Space Program.

    7. Which of the following is a hazard associated with sewer systems?

    a. Heat stress
    b. Electrocution
    c. Mechanical hazards
    d. Asbestos insulation

    Check your Work

    Read the material in each section to find the correct answer to each quiz question. After answering all the questions, click on the "Check Quiz Answers" button to grade your quiz and see your score. You will receive a message if you forgot to answer one of the questions. After clicking the button, the questions you missed will be listed below. You can correct any missed questions and check your answers again.



    In this video, Pennsylvania OSHA, in cooperation with Indiana University of Pennsylvania, PA OSHA director Sam Gualardo, discusses confined space safety in construction as part of their Focal Point Series.

    Final Exam

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