Confined spaces in construction

A confined space is any space that is large enough for a worker to enter, has limited or restricted means for entry or exit, and is not designed for continuous worker occupancy. To determine this you must evaluate each area on your site against these three criteria and document the results.

• Look for spaces like tanks, silos, vaults, crawlspaces, sewers, or pits.
• If the space is big enough for a person to enter, has a narrow opening or other restricted exits, and is not intended for someone to work inside for long periods, it meets the definition.

See the definition and evaluation requirements in 1926 Subpart AA for more details and to ensure you perform the required assessment.

A confined space becomes a permit-required confined space if it contains or has the potential to contain a hazardous atmosphere, has a material that could engulf an entrant, has an internal configuration that could trap or asphyxiate, or contains any other recognized serious safety or health hazard.

• Hazardous atmosphere examples: oxygen-deficient or oxygen-enriched atmospheres, flammable gases/vapors above safe levels, or toxic contaminant concentrations above exposure limits.
• Engulfment includes liquids or flowing granular materials that can bury or suffocate a worker.

You must identify and classify PRCS during your site evaluation and treat them under the permit system in 1926 Subpart AA.

The employer must develop and implement a written confined space program that covers how you identify confined spaces, classify permit-required confined spaces, control hazards, issue and manage entry permits, train employees, provide attendants and rescue, and coordinate among employers.

Key elements to include:

• Procedures for evaluating and reclassifying spaces;
• Permit system and required permit contents;
• Roles and responsibilities (entrants, attendants, entry supervisors);
• Testing and monitoring procedures for atmospheric hazards;
• Means of hazard control (ventilation, lockout, isolation);
• Rescue and emergency procedures and training;
• Coordination procedures when multiple employers are onsite.

Refer to 1926 Subpart AA for required program components and employer duties.

An entry permit must be used whenever employees are to enter a permit-required confined space (PRCS) to ensure hazards are identified and controlled before entry.

• The permit documents the space, hazards, results of atmospheric testing, required precautions, authorized entrants, attendant, entry supervisor, rescue arrangements, and the permit duration.
• The permit must be available at the site of entry and must be canceled when the entry is complete or conditions change.

See the permit and record requirements in 1926 Subpart AA.

Atmospheric testing must at a minimum evaluate oxygen content, flammable gases and vapors, and potential toxic air contaminants, and it must be done before entry and continuously or periodically during entry as needed.

• Test for oxygen (to ensure it is within safe limits), flammability (e.g., percent of lower explosive limit), and specific toxic contaminants anticipated in the space.
• Use properly calibrated and appropriate instruments and have trained personnel perform testing.
• Continue monitoring when operations or conditions change, when ventilation is used, or when activities could create hazards.

For required testing practices and monitoring, see 1926 Subpart AA.

An attendant must be an individual assigned to remain immediately outside the permit-required confined space to monitor conditions and protect the entrants; they must be trained and knowledgeable about the hazards and procedures.

Primary duties include:

• Keeping continuous visual or voice contact with entrants and monitoring conditions;
• Notifying entrants and the entry supervisor if a hazardous condition arises;
• Calling for rescue if necessary and summoning emergency services;
• Performing no other duties that interfere with their monitoring role.

Attendant responsibilities and qualifications are specified in 1926 Subpart AA.

Employees must receive training that assures they understand the hazards, safe work procedures, use of equipment, emergency procedures, and their specific duties (entrant, attendant, entry supervisor).

• Training must be provided before the employee performs duties in a confined space and whenever there is reason to believe the employee's skills or knowledge are inadequate (e.g., following an incident or when procedures change).
• Employers must certify training, including the employee's name, trainer, and date.

Training requirements and duties for each role are described in 1926 Subpart AA.

Rescue services must be capable of responding to a confined space emergency in a timely manner and must be trained and equipped to perform effective rescue without creating additional hazards.

• Employers must ensure that rescue personnel are trained in confined-space rescue techniques, use of rescue equipment, and basic life support as necessary.
• If using an outside rescue service, verify their ability to respond promptly and practice rescue plans with them before entry operations begin.

Requirements for rescue and emergency services are provided in 1926 Subpart AA.

A permit-required confined space can be reclassified to a non-permit confined space only when the employer can demonstrate that all hazards in the space have been eliminated or fully controlled such that no actual or potential hazardous atmosphere, engulfment, or other recognized hazards remain.

• Elimination means the hazard is removed (for example, by isolation of energy sources and ventilation that permanently removes the hazard), not merely controlled while workers are inside.
• The employer must document and justify the reclassification before allowing entry without a permit.

See reclassification and hazard elimination guidance in 1926 Subpart AA.

At minimum, an entry permit must identify the confined space, list the hazards of the space, state measures taken to isolate or control hazards, document atmospheric testing results, name authorized entrants, attendant, and entry supervisor, include rescue arrangements, and specify the permit duration.

• The permit should also list required personal protective equipment (PPE), ventilation procedures, and any special work procedures (e.g., hot work or lockout).
• The permit must be available at the worksite and be canceled once the entry is complete or conditions change.

Refer to permit content and handling requirements in 1926 Subpart AA.

The entry supervisor is responsible for authorizing entry into a permit-required confined space, ensuring that required precautions are in place, overseeing the entry, and canceling the permit when the entry is complete or unsafe conditions arise.

• They verify pre-entry checks, confirm atmospheric testing, ensure attendants and entrants are trained and equipped, and stop work if conditions change or the permit expires.
• The entry supervisor must be identified on the permit and must be competent to perform these tasks.

See role and responsibilities for entry supervisors in 1926 Subpart AA.

To control hazardous atmospheres you should eliminate or isolate the source of the hazard where possible, use continuous forced ventilation to dilute and remove contaminants, and conduct atmospheric testing before and during entry to confirm safe conditions.

• Ventilation should be mechanical and designed to change the air in the space sufficiently; however, ventilation alone may not be adequate for all contaminants.
• If hazards cannot be eliminated, use a full permit system with PPE, monitoring, and rescue procedures.

Guidance on controlling atmospheric hazards is included in 1926 Subpart AA.

Lockout/tagout or other positive isolation is required whenever an energy source (mechanical, electrical, hydraulic, pneumatic, chemical, etc.) could expose entrants to harm, and you must isolate those sources before entry to eliminate the hazard.

• Isolation can include blind/flange blanking, disconnecting and locking out power, or otherwise securing equipment so it cannot be energized while workers are inside.
• When isolation is part of the control strategy, it must be clearly documented on the permit and verified by the entry supervisor.

See isolation and hazard control requirements in 1926 Subpart AA.

When multiple employers are working at the same site, the host employer must inform contractors of the hazards and coordinate activities so that all employees are protected; each employer shares responsibility for implementing and following the confined space program.

• The host employer should identify confined spaces, communicate hazards and control measures to incoming contractors, and coordinate permits, rescue arrangements, and training.
• Contractors must follow the host's program or establish their own equivalent protections and coordinate with other employers to avoid conflicting actions.

See multi-employer coordination and communication requirements in 1926 Subpart AA.

Entrants must use a retrieval system (a body harness and retrieval line) unless the employer can demonstrate that using such a system would increase the overall risk (for example, create entanglement hazards or obstruct entry).

• Retrieval systems must be rigged to safely and quickly remove an incapacitated entrant without requiring a rescuer to enter the space.
• If a retrieval system is not used, the employer must document why and provide an alternative rescue plan that ensures timely non-entry rescue.

See retrieval and non-entry rescue requirements in 1926 Subpart AA.

Atmospheric monitoring must be performed before entry and then as often as necessary during the entry to ensure conditions remain safe—continuous monitoring is required whenever conditions can change or when ventilation or work activities may create hazards.

• If the atmosphere is stable and controls are effective, periodic rechecks may be acceptable, but continuous monitoring is recommended for operations that generate contaminants or where conditions fluctuate.
• Any unexpected readings or changes in conditions require immediate action, including evacuation and reassessment.

See monitoring and testing guidance in 1926 Subpart AA.

You must keep records that document training (who was trained, the trainer, and the date) and retain permits or documentation showing that hazards were evaluated and controlled for each permit-required confined space entry as required by your program.

• Training certification should include employee name, trainer, date, and subject of training.
• Entry permits or equivalent documentation should be maintained as specified by your program and local requirements and should include atmospheric test results and verification of hazard control.

Recordkeeping requirements and best practices are discussed in 1926 Subpart AA.

Hot work in or near a confined space must be controlled through the permit system, with hazards evaluated and appropriate precautions implemented such as isolating flammable materials, ensuring proper ventilation, using fire watches, and confirming atmospheric tests are safe.

• Hot work permits and additional controls (fire suppression, isolation of fuel sources, continuous atmospheric monitoring) should be part of the confined space permit when applicable.
• If hot work creates or increases atmospheric or fire hazards, entries must be suspended until hazards are eliminated.

See combined hazard control and permit requirements in 1926 Subpart AA.

No — a single person cannot simultaneously serve as both an attendant and an entrant because the attendant must remain outside the confined space to monitor and protect entrants.

• Attendants must be dedicated to their monitoring role and not perform duties that would remove them from that responsibility.
• If staffing is limited, you must provide additional personnel or arrange alternative protective measures (like continuous monitoring and rescue readiness) that comply with the standard.

See role separation and attendant duties in 1926 Subpart AA.

If atmospheric testing detects unsafe readings, immediately evacuate all entrants, secure the space, and re-evaluate controls and testing procedures before any re-entry is allowed.

• Take corrective measures such as increasing ventilation, eliminating the contaminant source, or using appropriate respiratory protection and then re-test to confirm safe conditions.
• The entry supervisor must cancel the existing permit if conditions change and re-authorize entry only after hazards are corrected and documented.

Follow the emergency and re-entry procedures in 1926 Subpart AA.

Contractors and the host employer must coordinate so that hazards are identified, information about spaces and control measures is shared, and work is sequenced and protected to avoid conflicts or unsafe conditions.

• The host employer should inform contractors of the locations and hazards of confined spaces and the protective measures in place; contractors should communicate their planned operations and additional hazards they introduce.
• Jointly agree on permits, rescue arrangements, isolation procedures, and communication protocols before work begins.

See coordination and information-sharing requirements in 1926 Subpart AA.

Yes — instruments used for atmospheric testing must be appropriate for the contaminants being measured, properly maintained and calibrated, and operated by trained personnel.

• Calibration and bump-testing should be performed according to the manufacturer's instructions and your program's procedures.
• Only trained employees or qualified contractors should perform the testing and interpret the results for entry decisions.

Instrument use and testing requirements are addressed in 1926 Subpart AA.

To control engulfment hazards you must prevent the buildup or movement of materials that could bury or trap workers by isolating the hazard, using barriers or shoring, stopping flow of materials, and using retrieval systems and rescue planning before entry.

• Never enter a space where a flowing or loose material could shift and engulf a worker unless the hazard is eliminated or appropriate controls are in place and documented on the permit.
• Use retrieval systems and coordinate rescue arrangements that account for possible engulfment scenarios.

See hazard identification and control requirements for engulfment in 1926 Subpart AA.

Yes — attendants need training so they can recognize an emergency and summon rescue services quickly, but they are not expected to perform complex rescues; rescue teams or services must be trained and equipped separately.

• Attendants must know how to call for help, initiate the rescue plan, and perform non-entry rescues if trained and if the procedure is part of the employer's plan.
• Employers must ensure rescue personnel have the specific confined-space rescue training and equipment necessary for the hazards present.

See attendant duties and rescue requirements in 1926 Subpart AA.

Ventilation can be used to control hazardous atmospheres and, if it eliminates the hazard, may allow reclassification, but relying solely on ventilation while hazards remain requires that you follow the full permit system and continuous monitoring.

• If ventilation permanently and verifiably eliminates the hazard (not just while workers are present), you may reclassify the space; otherwise, use a permit and continuous or periodic monitoring to ensure safety.
• The employer must document the effectiveness of ventilation and maintain testing records.

See ventilation, control measures, and reclassification guidance in 1926 Subpart AA.

If conditions worsen, the attendant or entry supervisor must immediately order evacuation of the confined space, account for all entrants, and activate rescue and emergency procedures as required by your program.

• Entrants must exit the space immediately upon alarm, change in conditions, or direction from the attendant or entry supervisor.
• After evacuation, do not re-enter until the cause is identified and corrective action is completed and documented.

See emergency actions and evacuation procedures in 1926 Subpart AA.

Yes — you must take steps to prevent unauthorized entry into permit-required confined spaces, which commonly includes posting warning signs, using barriers, or locking access points to keep untrained workers out.

• Signs should communicate the hazard and that entry is restricted to authorized, trained personnel only.
• Controls to prevent unauthorized entry must be maintained for as long as the hazard exists.

See access control and posting requirements in 1926 Subpart AA.

Before entry, the employer must verify that energy isolation measures (such as lockout/tagout, blanking, or disconnecting) are effective by testing or other positive methods to ensure equipment cannot be energized or materials cannot flow into the space.

• Verification may include trying controls under safe conditions, using test instruments, or confirming valves are secured and locks are in place.
• The verification step must be documented and noted on the entry permit before entry begins.

See energy control and verification requirements in 1926 Subpart AA.

A rescue plan must identify the rescue method (non-entry retrieval or trained rescue team), required rescue equipment, communications and alarm procedures, response times, and training and practice requirements to ensure timely and effective rescues.

• The plan should consider the specific hazards of the space and be coordinated with any external emergency responders.
• Employers must periodically practice rescue procedures and confirm that rescue services can meet response time requirements.

See rescue planning and coordination requirements in 1926 Subpart AA.