Permit-required confined spaces

A confined space is a permit-required confined space if it meets the confined-space criteria and has one or more permit hazards (so you must evaluate each space). See the definition of a confined space and permit-required confined space in 1910.146(b) and follow the employer evaluation requirement in 1910.146(c)(1).

• Check the three confined-space elements: large enough to enter, limited entry/exit, and not designed for continuous occupancy (1910.146(b)).
• Then check for permit hazards (hazardous atmosphere, engulfment potential, inwardly converging walls/floor that could trap, or any other recognized serious hazard) (1910.146(b)).
• Use the decision flow chart in Appendix A to 1910.146 to document your evaluation, as 1910.146(c)(1) suggests.

A permit-required confined space is a confined space that contains or has the potential to contain a hazardous atmosphere, engulfing material, an internal configuration that could trap or asphyxiate an entrant, or any other recognized serious safety or health hazard. See the full definition and the listed characteristics in 1910.146(b).

• "Confined space" elements: large enough to enter, limited entry/exit, not designed for continuous occupancy (1910.146(b)).
• Permit hazards include: hazardous atmospheres (flammable gas/vapor >10% LFL, oxygen <19.5% or >23.5%, toxic substances above PELs), potential for engulfment, inwardly converging walls or tapered floors, or other recognized serious hazards (1910.146(b)).

Employers must inform exposed employees of the existence, location, and danger of permit spaces by posting danger signs or by any other equally effective means. See 1910.146(c)(2).

• A sign such as "DANGER - PERMIT-REQUIRED CONFINED SPACE, DO NOT ENTER" would meet the requirement, but employers may use alternatives (training, tags, locked covers) if they are equally effective (1910.146(c)(2)).

If employees will not enter permit spaces, you must take effective measures to prevent employee entry and still comply with the evaluation, employee notification, provisions about reclassification, and communication requirements listed in [1910.146(c)(3)]. Specifically, you must comply with [1910.146(c)(1)], [1910.146(c)(2)], [1910.146(c)(6)], and [1910.146(c)(8)]. See 1910.146(c)(3).

• Effective measures can include locking or removing covers, posting signs, training, or physical barriers to stop unauthorized entry.
• You still must evaluate spaces, inform employees of hazards, ensure any necessary isolation/control measures are in place, and communicate hazards to contractors or other employers on site (1910.146(c)(1),(2),(6),(8)).

The employer must develop and implement a written permit space program when employees will enter permit spaces, and this written program must be available for inspection by employees and their authorized representatives. See 1910.146(c)(4).

• The written program should describe procedures for identifying permit spaces, controlling hazards, issuing permits, training, monitoring, emergency/rescue procedures, and returning spaces to service (see related requirements in 1910.146(d)–(k)).
• Make the program available at the workplace for entrants, attendants, entry supervisors, and their authorized employee representatives (1910.146(c)(4)).

An entry permit must list the measures taken to ensure acceptable entry conditions and the information required by the standard's permit system—such as the space to be entered, purpose of entry, authorized entrants, attendants, entry supervisor, hazards, control measures, testing results, personal protective equipment, communication and rescue arrangements, and the permit duration. See the permit requirements in 1910.146(f).

• Typical items on the permit include: location, reason for entry, date/time, authorized entrants, attendant, entry supervisor, atmospheric test results (oxygen, flammable, toxic), ventilation/controls used, required PPE, rescue and emergency services, and signatures/authorization (1910.146(f)).

An employer may use the alternate procedures only when the employer can demonstrate that the only hazard posed by the permit space is an actual or potential hazardous atmosphere, continuous forced-air ventilation alone is sufficient to maintain the space safe for entry, and the employer documents monitoring/inspection data supporting those demonstrations and meets the other conditions in [1910.146(c)(5)(i)(A)–(F)]. See 1910.146(c)(5)(i).

• Key required demonstrations include: (A) atmosphere is the only hazard; (B) continuous forced-air ventilation is sufficient; (C) monitoring/inspection data support A and B; (D) if an initial entry is needed to obtain that data, it must be done under full permit procedures; (E) determinations and data must be documented and provided to entrants or their representatives; and (F) entry under alternate procedures must follow 1910.146(c)(5)(ii).

When using alternate procedures under 1910.146(c)(5)(ii), you must meet the procedural steps specified there—such as testing for atmospheric hazards before entry, continuous ventilation during entry, monitoring of the atmosphere as necessary, and having a means (like a retrieval system) to get entrants out if conditions change. See 1910.146(c)(5)(ii) for full details.

• Typical actions include: initial testing to show ventilation will control the atmosphere, continuous forced air ventilation while entrants are inside, periodic monitoring to ensure safe levels, and written documentation of the supporting data and procedures.

Acceptable entry conditions are the set of conditions that must exist in a permit space to allow safe entry and work by authorized entrants; the employer must ensure and document these conditions before allowing entry. See the definition of "acceptable entry conditions" in 1910.146(b).

• Acceptable entry conditions include verified atmospheric conditions (oxygen, flammable, toxic) within safe ranges and that other hazards (mechanical, engulfment, electrical) are controlled by isolation, lockout/tagout, blanking, or other measures (1910.146(b)).

You must test for atmospheric hazards that could affect entrants—at a minimum oxygen concentration, flammability (percent of LFL), and suspected toxic contaminants—and continue monitoring as needed during entry to ensure conditions remain acceptable. See the testing definition and the general requirements in 1910.146(c).

• The standard defines "testing" as identifying and evaluating hazards and specifying tests to be performed in the permit space (1910.146(c)).
• Test for oxygen (must be between 19.5% and 23.5%), flammability (<10% LFL) and any substances with PELs listed in subpart G or Z that could exceed limits in the space (1910.146(b)).
• If you rely on OSHA PELs or dose limits for toxic contaminants, consult the relevant standards in 29 CFR 1910 subpart Z or G, and use Safety Data Sheets under the Hazard Communication Standard 1910.1200 to help identify contaminants.

Yes — continuous forced-air ventilation can be the sole method of making a permit space safe for entry only if the employer demonstrates that an actual or potential hazardous atmosphere is the only hazard and that continuous forced-air ventilation alone is sufficient to maintain safe conditions, with supporting monitoring and documentation. See 1910.146(c)(5)(i)(A)–(C).

• If these conditions are met, the employer may use the alternate procedures in 1910.146(c)(5)(ii), but must document monitoring/inspection data and make it available to entrants (1910.146(c)(5)(i)(C),(E)).

An "entry" begins as soon as any part of an entrant's body breaks the plane of an opening into the permit space. See the definition of "entry" in 1910.146(b).

• This definition means you must have all required controls, monitoring, attendants, permits, and rescue arrangements in place before any part of the entrant crosses that opening (1910.146(b)).

An attendant is an individual stationed outside one or more permit spaces who monitors authorized entrants and performs all attendant duties assigned in the employer's permit space program. The attendant must maintain communication, monitor conditions, summon rescue if needed, and not enter the space to attempt rescue unless properly trained and equipped. See the definitions in 1910.146(b) and attendant duties in 1910.146(h).

• Duties include keeping track of entrants, monitoring atmospheric and physical conditions, ordering evacuation if a prohibited condition arises, summoning rescue services, and performing non-entry rescue only if authorized and trained (1910.146(h)).

Employers must ensure that rescue services are available, that rescuers are trained and equipped for the specific hazards of the permit space, and that a means for non-entry rescue (such as a retrieval system) is provided unless it increases risk; see 1910.146(k) and the definition of retrieval system in 1910.146(b).

• Rescue services can be in-house or provided by a contracted rescue team, but they must be capable of responding promptly and performing the rescue without putting additional employees at risk (1910.146(k)).
• Provide retrieval equipment (harness, retrieval line, lifting device/anchor) for non-entry rescue when feasible, and ensure rescuers are trained to use it (1910.146(b),(k)).

An entry supervisor is the person responsible for determining if acceptable entry conditions exist, authorizing entry, overseeing entry operations, and terminating entry; the employer may assign the role to the employer, foreman, crew leader, or another trained individual and the duties may be transferred during an entry. See the definition and guidance in 1910.146(b) and the requirement to comply with related procedures in 1910.146(c)(6).

• The entry supervisor may also serve as attendant or authorized entrant if trained and equipped for each role (1910.146(b)).
• The entry supervisor signs or otherwise approves entry permits, ensures controls are in place, and halts entry if conditions become unsafe (1910.146(f),(c)(6)).

Before authorizing entry, employers must isolate and control hazards by methods such as blanking/blinding, misaligning or removing sections of lines, double block and bleed, lockout/tagout, or blocking/disconnecting mechanical linkages to eliminate the release of energy and materials into the space. See the definition of "isolation" and related provisions in 1910.146(b) and the control requirements in 1910.146(d).

• Use blanking or blinding where appropriate to absolutely close a line, and consider double block and bleed systems for piping that cannot be physically removed (1910.146(b)).
• Where isolation of the hazard is not possible, provide other protective measures (e.g., ventilation, PPE) as specified in the permit-space program (1910.146(d)).

Just before entry, the entry supervisor must ensure that testing has been conducted to determine and document that acceptable entry conditions exist—this includes testing for oxygen, flammability, and toxic contaminants as appropriate—and that monitoring continues as necessary while entrants are inside. See 1910.146(e).

• Conduct initial atmospheric testing outside and at various levels within the space for oxygen, flammables (<10% LFL), and toxic contaminants (relative to PELs) and record results on the entry permit (1910.146(e)).
• If ventilation or other controls are used, verify they achieve acceptable conditions and continue monitoring during entry to detect any changes (1910.146(e)).

An entry permit must be canceled when the entry is completed or when a condition that is not allowed by the permit arises, and the permit space may be returned to service once the employer has terminated entry and taken steps to ensure the space is safe for normal operations. See 1910.146(j).

• Cancel the permit when work is finished, when entrants leave, or if a prohibited condition occurs; retain the permit as part of records per your written program (1910.146(j)).
• Follow your permit-space program procedures to return the space to service (e.g., remove isolation devices, restore systems) only after ensuring it is safe to re-energize or use the space.

Employers must inform contractors about the existence and location of permit spaces and the hazards they present, and coordinate entry operations so that all employers on site understand the hazards and measures in place to protect entrants. See the multi-employer communication requirement in 1910.146(c)(8).

• Share information about the permit space program, hazards, required controls, PELs, entry procedures, rescue arrangements, and any special precautions.
• Coordinate control measures (lockout/tagout, isolation, ventilation) and ensure contractors follow your permit procedures or have compatible procedures before allowing entry (1910.146(c)(8)).

"Engulfment" is when a person is surrounded and effectively captured by a liquid or flowable solid that can fill or block the respiratory system or exert enough force to cause death by strangulation, constriction, or crushing, and it is a serious hazard when a permit space contains materials (like grain, sand, liquids) that could flow and cover or trap an entrant. See the definition in 1910.146(b).

• If a permit space contains bulk materials that can shift, flow, or collapse and bury a person, control measures (isolation, barriers, or special rescue plans) must be in place before entry (1910.146(b)).

"Blanking or blinding" is the absolute closure of a pipe, line, or duct by fastening a solid plate that completely covers the bore and can withstand system pressure, and it should be used when you need a positive mechanical isolation to prevent materials or energy from entering the permit space. See the definition in 1910.146(b).

• Use blanking/blinding where practical instead of less positive methods (like single valve closure) to ensure the space is isolated from hazardous substances or pressures (1910.146(b)).

"Inerting" means displacing the atmosphere in a permit space with a noncombustible gas (like nitrogen) to make the atmosphere noncombustible, but inerting can produce an oxygen-deficient atmosphere (below 19.5%) that is immediately dangerous to life or health (IDLH). See the definition and the note about inerting in 1910.146(b).

• The standard specifically notes that inerting produces an IDLH oxygen-deficient atmosphere; such atmospheres require respiratory protection and rescue planning under other OSHA standards (e.g., see the discussion of oxygen-deficient atmospheres in OSHA's interpretation at https://www.osha.gov/laws-regs/standardinterpretations/2024-07-16).

If an initial entry into a permit space is necessary to obtain monitoring/inspection data to support alternate procedures, that first entry must be performed under the full permit procedures in paragraphs (d)–(k); you cannot use alternate procedures for that initial data-gathering entry. See 1910.146(c)(5)(i)(D).

• That means you must follow the written permit program, have attendants, an authorized entry team, atmospheric testing, rescue arrangements, and a signed permit for the initial entry (1910.146(d)–(k)).

The determinations and supporting monitoring/inspection data that justify using alternate procedures must be documented by the employer and made available to each employee who enters under those alternate procedures (or that employee's authorized representative) before the entry. See 1910.146(c)(5)(i)(E).

• Keep records of the monitoring data, ventilation plans, and inspection data and provide them to entrants so they understand the basis for relying solely on continuous forced-air ventilation (1910.146(c)(5)(i)(E)).

IDLH is any condition that poses an immediate or delayed threat to life, would cause irreversible adverse health effects, or would interfere with an individual's ability to escape unaided; recognizing IDLH atmospheres matters because such conditions require specialized rescue planning, equipment, and trained rescue personnel. See the definition of IDLH in 1910.146(b).

• OSHA's interpretation on oxygen-deficient atmospheres explains that oxygen-deficient conditions are considered IDLH and that employers must follow respiratory protection and rescue requirements when IDLH conditions are possible (see https://www.osha.gov/laws-regs/standardinterpretations/2024-07-16).
• If a space could become IDLH, non-entry rescue may be required and rescue teams must be capable of operating in IDLH atmospheres (1910.146(k)).

You must test the space's internal atmosphere for oxygen content first, then flammable gases and vapors, and then potential toxic contaminants with a calibrated direct-reading instrument before anyone enters. The employer must provide each entrant or that employee's authorized representative an opportunity to observe the pre-entry testing in accordance with 1910.146(c)(5)(ii)(C).

Employees may enter only after the continuous forced air ventilation has eliminated any hazardous atmosphere in the space. The ventilation must be directed to the areas where employees will be present, must continue until all employees leave, and the air must come from a clean source that does not increase hazards, per 1910.146(c)(5)(ii)(E).

You must keep the forced air ventilation operating until all employees have left the space. The standard requires the ventilation to continue for the duration of the entry so it keeps the immediate areas where employees work free of hazardous atmospheres, as stated in 1910.146(c)(5)(ii)(E)(2).

You must periodically test the atmosphere as necessary to ensure the continuous forced air ventilation is preventing hazardous atmosphere accumulation, and entrants or their representatives must be allowed to observe that periodic testing. This requirement is in 1910.146(c)(5)(ii)(F).

If a hazardous atmosphere is detected, each employee must leave the space immediately, you must evaluate how the hazardous atmosphere developed, and you must implement measures to protect employees before any re-entry. These steps are required by 1910.146(c)(5)(ii)(G).

Any conditions that would make it unsafe to remove the entrance cover must be eliminated before the cover is removed. The standard requires elimination of those unsafe conditions prior to removal per 1910.146(c)(5)(ii)(A).

When an entrance cover is removed, you must promptly guard the opening with a railing, temporary cover, or other temporary barrier to prevent accidental falls through the opening and to protect entrants from foreign objects entering the space, as required by 1910.146(c)(5)(ii)(B).

The employer must verify the space is safe and that the required pre-entry measures have been taken with a written certification that includes the date, location of the space, and the signature of the person providing the certification; that certification must be made before entry and be available to each entrant or their authorized representative, as set out in 1910.146(c)(5)(ii)(H).

A permit space may be reclassified as a non-permit confined space if it poses no actual or potential atmospheric hazards and all hazards in the space are eliminated without entry; it remains non-permit only as long as those non-atmospheric hazards remain eliminated, per 1910.146(c)(7)(i).

No. Control of atmospheric hazards by forced air ventilation does not constitute elimination of hazards for reclassification; if entry is needed to eliminate hazards, it must be done under the full permit program in paragraphs (d)–(k), and only when testing shows hazards are eliminated can the employer reclassify the space as non-permit for as long as hazards remain eliminated, as explained in 1910.146(c)(7)(ii).

You must document the basis for determining that all hazards have been eliminated with a certification that includes the date, location of the space, and signature of the person making the determination; the certification must be made available to each entrant or their authorized representative, per 1910.146(c)(7)(iii).

If hazards arise in a space that was declassified under paragraph (c)(7), each employee in the space must exit the space immediately, consistent with 1910.146(c)(7)(iv).

A host employer must inform the contractor that the workplace contains permit spaces and that entry is allowed only through a permit program that meets the standard; apprise the contractor of hazards and precautions, coordinate entry operations when both will be working in or near the spaces, and debrief the contractor after operations, per 1910.146(c)(8).

A contractor must obtain any available information about permit space hazards and entry operations from the host employer, coordinate entry operations when personnel from both employers will be in or near permit spaces, and inform the host employer about the contractor's permit program and any hazards encountered or created, as required by 1910.146(c)(9).

A permit space program must prevent unauthorized entry, identify and evaluate permit space hazards, and develop and implement procedures and practices for safe entry operations—this includes specifying acceptable entry conditions, isolating the space, ventilating or purging to control atmospheric hazards, providing barriers, and verifying acceptable conditions throughout the entry, per 1910.146(d)(1)–(3).

Employers must provide, maintain, and ensure proper use of necessary equipment at no cost, including testing and monitoring instruments, ventilating equipment, communication devices, personal protective equipment, lighting, barriers, ladders for safe ingress/egress, and rescue/emergency equipment (unless provided by rescue services), according to 1910.146(d)(4).

When testing for atmospheric hazards you must test first for oxygen, then for combustible gases and vapors, and then for toxic gases and vapors; you must test before authorization to enter and monitor as necessary during entry to ensure acceptable conditions are maintained, per 1910.146(d)(5).

Authorized entrants or their authorized representatives must be given the opportunity to observe pre-entry and subsequent testing, must be provided immediate results of any testing, and can request a reevaluation of the permit space if they believe the initial evaluation was inadequate; see 1910.146(d)(5)(iv)–(vi).

You must provide at least one attendant outside the permit space for the entire duration of entry operations, and an attendant may monitor more than one permit space only if they can effectively perform the duties required by paragraph (i) for each space, as required in 1910.146(d)(6).

Yes. OSHA recognizes oxygen-deficient atmospheres as immediately dangerous to life or health (IDLH) and civilian employees covered by OSHA must follow respiratory protection requirements in 29 CFR 1910.134 when such atmospheres are present, as discussed in OSHA's interpretation on oxygen-deficient atmospheres in HVAC systems at https://www.osha.gov/laws-regs/standardinterpretations/2024-07-16 and in 1910.134.

Under 1910.146(e)(6) canceled entry permits must be retained for at least 1 year to support program review and correction. Employers must keep each canceled entry permit for a minimum of one year so that the permit-required confined space program can be reviewed using those canceled permits as required by 1910.146(d)(14).

• Purpose: Retaining permits documents any problems or anomalies encountered during entry operations so the employer can identify and correct deficiencies before future entries (1910.146(e)(6)).
• Practical tip: Note issues on the permit (equipment failures, unauthorized entries, unexpected hazards, near-misses) so they are available during the annual or event-driven program review required by 1910.146(d)(14).

Under 1910.146(f) an entry permit must identify the space, purpose, duration, people involved, hazards, control measures, and supporting arrangements listed in the standard. The permit must include the elements spelled out in 1910.146(f)(1)–(f)(15), including:

• The permit space to be entered (1910.146(f)(1)).

• The purpose of entry (1910.146(f)(2)).

• Date and authorized duration (1910.146(f)(3)).

• Authorized entrants and a method to track who is inside (1910.146(f)(4)).

• Names of attendants and entry supervisor (1910.146(f)(5)–(f)(6)).

• Hazards, measures to isolate/control them, and acceptable entry conditions (1910.146(f)(7)–(f)(9)).

• Results of initial and periodic atmospheric tests with tester initials and times (1910.146(f)(10)).

• Rescue/emergency services and how to summon them, communications, required equipment, and any additional applicable permits (e.g., hot work) (1910.146(f)(11)–(f)(15)).

• Practical tip: Use Appendix D examples but ensure the permit reflects site-specific hazards and controls referenced in 1910.146(f).

Under 1910.146(i)(4) an attendant may enter a permit space to attempt a rescue only if the employer's program allows attendant entry for rescue and the attendant has been trained, equipped, and relieved as required; rescue capability must also meet the requirements of 1910.146(k)(1).

• Key conditions: The attendant must be trained and equipped for rescue operations under 1910.146(k)(1) and must be relieved by another attendant before entering the space (1910.146(i)(4)).
• Rescue selection and capability: The employer must evaluate prospective rescuers for timely response and proficiency and select teams that can reach victims within an appropriate timeframe and are equipped and proficient for the specific permit-space hazards (1910.146(k)(1)(i)–(k)(1)(iii)).
• Practical implication: Do not rely on an attendant to self-rescue entrants unless they have documented rescue training, equipment, and a plan that meets 1910.146(k)(1).

Under 1910.146(d)(7) the permit program must include procedures that let one attendant monitor multiple permit spaces without being distracted from the attendant duties listed in 1910.146(i). In practice the program must describe how the attendant will continuously perform required functions — counting entrants, monitoring conditions, communicating, ordering evacuations, summoning rescue, and preventing unauthorized entry — for each space they monitor (1910.146(d)(7); 1910.146(i)).

• Examples of required controls and procedures: staggered work schedules, reliable communications, clear visual line-of-sight or video monitoring, written checklists, immediate relief arrangements, and explicit emergency-response steps so the attendant can respond to an emergency in one space without losing control of others.
• Employer responsibility: If the attendant cannot "effectively and safely perform all the duties" described in 1910.146(i), the attendant must order evacuation and the program must be revised per 1910.146(d)(13).

Under 1910.146(g)(4) the employer must certify that employees received the required confined-space training and keep a certification that lists each employee's name, the trainer's signatures or initials, and the dates of training; these records must be available for inspection by employees and their authorized representatives. The certification required by 1910.146(g)(4) documents that training required in 1910.146(g) was completed.

• Required contents: each employee's name, trainer signature/initials, and training dates (1910.146(g)(4)).
• Accessibility: make the certification available for inspection by employees and their authorized representatives (for example, union reps or designated safety representatives) as specified in the standard.
• Practical tip: keep training certificates current and retrain/recertify employees when duties change, when procedures change, or when the employer has reason to believe the employee's knowledge or use of procedures is inadequate (1910.146(g)(2)).