Compressed air safety requirements

Under 1926.803(a)(1), a competent person designated by the employer must be present at all times and is responsible for full compliance with the compressed air subpart.

• That person must be familiar with this entire subpart and represent the employer on-site.
• They are responsible for ensuring work practices, medical supervision, lock operations, communications, and records meet the requirements in 1926.803(a)(1) and related paragraphs.

Under 1926.803(a)(2), every employee must be instructed in the rules and regulations that concern their safety or the safety of others when working in compressed air.

• Training should cover compression/decompression procedures, use of man locks, signals and communications, how to report discomfort, and emergency procedures.
• Employers must ensure the instruction is understandable and provided before the employee enters compressed-air work, as required by 1926.803(a)(2).

Under 1926.803(b)(1), employers must retain one or more licensed physicians experienced in the medical aspects of compressed-air work and decompression illness, and the physician must be available at all times while work is in progress.

• The retained physician must be willing and physically able to enter a pressurized environment if needed.
• This physician provides medical supervision for compressed-air employees and must be available on-site during operations as described in 1926.803(b)(1).

No. Under 1926.803(b)(2), an employee may not enter a compressed-air environment until a licensed physician has examined them and reported that they are physically qualified for such work.

• Employers must obtain and keep the physician's report before permitting entry.
• This helps prevent medical complications related to pressure exposure as required by 1926.803(b)(2).

Under 1926.803(b)(3), if an employee is absent from work for 10 days or absent due to sickness or injury, they must be reexamined by the physician and cleared before resuming compressed-air work.

• This ensures changes in health that could increase risk are identified before return.
• Employers should coordinate with the retained physician to obtain the reexamination report per 1926.803(b)(3).

Under 1926.803(b)(4), an employee continuously employed in compressed air must be reexamined by the physician at intervals designated by that physician, but not to exceed once per year.

• The physician sets the specific reexamination interval based on individual needs, with at least annual exams.
• Maintain records of these exams as required by 1926.803(b)(4).

Under 1926.803(b)(5) and (6), the retained physician must keep complete records of examinations and of any decompression illness, injuries, or deaths, and those records must be available to OSHA and a copy forwarded to OSHA within 48 hours following an accident, death, injury, or decompression illness.

• Records must document causes, places where injured were taken, and other relevant details.
• Employers should have procedures to promptly transmit records to OSHA as required by 1926.803(b)(5) and 1926.803(b)(6).

Under 1926.803(b)(7) and (8), a fully equipped first aid station must be provided at each tunnel project regardless of crew size, and if tunnels are excavated from portals more than 5 road miles apart, a first aid station and transportation facilities must be provided at each portal.

• Employers must also have an ambulance or transportation suitable for a litter case at each project as part of these requirements.
• See 1926.803(b)(7) and 1926.803(b)(8).

Under 1926.803(b)(9), a medical lock must be established and maintained in immediate working order whenever the air pressure in the working chamber is increased above normal atmospheric pressure.

• The medical lock must be ready for immediate use during pressurized operations to treat decompression illness and related emergencies.
• See 1926.803(b)(9).

Under 1926.803(b)(10)(i), a medical lock must have at least 6 feet of clear headroom at the center and be subdivided into not less than two compartments.

• This ensures adequate space for patients and attendants and supports separate functions (e.g., treatment and observation).
• See the dimensional and subdivision requirement in 1926.803(b)(10)(i).

Under 1926.803(b)(10)(ii) and (iii), the medical lock must be readily accessible to employees working under compressed air and kept ready for immediate use for at least 5 hours after any employee emerges from the working chamber.

• Employers should position the lock so it can be quickly reached and ensure it remains operational for the specified post-emergence period.
• See 1926.803(b)(10)(ii) and 1926.803(b)(10)(iii).

Under 1926.803(b)(10)(iv) and (v), the medical lock must be properly heated, lighted, and ventilated and must be maintained in a sanitary condition.

• Maintain temperature, lighting, ventilation, and cleaning schedules to ensure patient safety and comfort.
• See 1926.803(b)(10)(iv) and 1926.803(b)(10)(v).

Under 1926.803(b)(10)(vi) and (ix), the medical lock must have a nonshatterable port for constant observation of occupant(s) and be provided with air pressure gauges showing pressure within each compartment to observers inside and outside the lock.

• Ensure ports are durable and gauges are installed so both inside and outside observers can monitor pressures.
• See 1926.803(b)(10)(vi) and 1926.803(b)(10)(ix).

Under 1926.803(b)(10)(x) and (xi), the medical lock must be equipped with a manual-type sprinkler that can be activated inside the lock or by the outside lock tender, and oxygen lines must lead to external tanks with check valves to prevent reverse flow; the oxygen system inside must be closed-circuit and automatically shut off when the fire system activates.

• Maintain and test the sprinkler and oxygen systems and ensure check valves and automatic shutoffs work reliably.
• See 1926.803(b)(10)(x) and 1926.803(b)(10)(xi).

Under 1926.803(b)(10)(xii), the medical lock must be in constant charge of an attendant under the direct control of the retained physician, and that attendant must be trained in the lock's use and in treating decompression illness symptoms.

• The attendant must understand lock controls, emergency procedures, and steps for medical treatment as instructed by the physician.
• See 1926.803(b)(10)(xii).

Under 1926.803(b)(10)(xiii) and (xiv), the medical lock must be adjacent to an adequate emergency medical facility, and that facility must be equipped with demand-type oxygen inhalation equipment approved by the U.S. Bureau of Mines.

• Employers should verify adjacency to an emergency facility and that oxygen equipment meets the specified approval and functionality.
• See 1926.803(b)(10)(xiii) and 1926.803(b)(10)(xiv).

Under 1926.803(b)(10)(xv) and (xvi), the medical lock must be capable of being maintained between 70 °F and 90 °F when in use, and must have sources of air free of oil and carbon monoxide that can raise the air pressure in the lock from 0 to 75 p.s.i.g. within 5 minutes.

• Ensure air supply quality (no oil/CO) and pressure-raising capacity are regularly tested and maintained.
• See 1926.803(b)(10)(xv) and 1926.803(b)(10)(xvi).

Under 1926.803(b)(11), employers must furnish identification badges to all compressed-air workers and keep a permanent record of badges issued; the badge must list the employee's name, the medical lock address, the retained physician's telephone number, and instructions to rush the wearer to the medical lock in case of emergency or unexplained illness.

• Employers must also keep a permanent roster of badges and ensure employees wear badges both on and off the job.
• See 1926.803(b)(11).

Under 1926.803(c)(1), effective and reliable communication (bells, whistles, telephones, etc.) must be maintained at all times between the working chamber face; the working chamber side of the man lock near the door; the interior of the man lock; the lock attendant's station; the compressor plant; the first-aid station; the emergency lock (if required); and the special decompression chamber (if required).

• Employers should test and maintain these communication links so crew members and attendants can coordinate compression, decompression, and emergencies.
• See the full list in 1926.803(c)(1).

Under 1926.803(d)(1), the time of decompression for each man lock must be posted in the lock using the specified form showing pounds to pounds in minutes and signed by the superintendent.

• Post the decompression schedule in the man lock at all times so workers and attendants know the prescribed decompression rates.
• See the required posting format in 1926.803(d)(1).

Under 1926.803(d)(3) and 1926.803(e), for each 8-hour shift an outside employee must keep a record of employees under air pressure near the entrance showing the period each employee spends in the air chamber and the time taken from decompression, and a copy must be submitted to the appointed physician after each shift.

• Keep these records current and legible and provide copies to the physician as required.
• See 1926.803(d)(3) and the record submission requirement in 1926.803(e).

Under 1926.803(e)(1), every employee going under air pressure for the first time must be instructed on how to avoid excessive discomfort.

• Training should include equalizing ear/sinus pressure, recognizing and reporting pain or pressure, and when to signal the lock attendant.
• See 1926.803(e)(1).

Under 1926.803(e)(2) and (3), pressure shall not be increased more than 3 p.s.i.g. within the first minute and must be held at 3 p.s.i.g. and again at 7 p.s.i.g. long enough to check for discomfort; after the first minute the pressure may be raised uniformly at a rate not to exceed 10 p.s.i. per minute.

• Follow the hold points at 3 and 7 p.s.i.g. to monitor worker comfort and stop or reduce pressure if problems occur.
• See 1926.803(e)(2) and 1926.803(e)(3).

Under 1926.803(e)(4), if an employee complains of discomfort during compression, the pressure must be held to see if symptoms are relieved; if discomfort persists after 5 minutes, the attendant must gradually reduce pressure until the employee signals relief, and if no relief is indicated, reduce pressure to atmospheric and release the employee.

• The attendant must follow this procedure promptly to avoid injury and document the incident.
• See the required actions in 1926.803(e)(4).

Under 1926.803(e)(5), no employee shall be subjected to pressure exceeding 50 pounds per square inch except in an emergency.

• Design operations to keep pressure at or below 50 p.s.i.g. during normal work; document any emergency conditions that required exceeding this limit.
• See 1926.803(e)(5).

Under 1926.803(f)(1), decompression to normal condition must follow the Decompression Tables in Appendix A of this subpart.

• Employers and the retained physician must use the Appendix A tables to plan and execute decompression schedules, unless the physician has established alternative procedures for repetitive exposures or decanting as allowed in 1926.803(f)(2) and 1926.803(f)(3).
• See 1926.803(f)(1).

Under 1926.803(f)(2) and (3), the appointed physician is responsible for establishing decompression methods and procedures for repetitive exposures and must establish decanting procedures before any employee is decompressed by decanting methods.

• The physician decides safe procedures for multiple daily exposures and for decanting, including limits on time at atmospheric pressure between exposures.
• See 1926.803(f)(2) and 1926.803(f)(3).

Under 1926.803(g)(1)(i), except in an emergency, employees shall not pass from the working chamber to atmospheric pressure until after decompression in accordance with the procedures in this subpart.

• Employers must enforce decompression schedules and only allow emergency exceptions with appropriate medical oversight.
• See 1926.803(g)(1)(i).

Under 1926.803(g)(1)(ii) and (iii), the lock attendant must be under the direct supervision of the appointed physician and be stationed at the lock controls on the free-air side during compression and decompression, remaining there whenever men are in the working chamber or man lock; locks above 12 p.s.i.g. must have automatic controls to regulate decompressions (except where pressure is below 12 p.s.i.g.).

• The attendant must be trained, remain at the control station, and be able to override automatic controls in emergencies as required by 1926.803(g)(1)(ii) and 1926.803(g)(1)(iii).

Under 1926.803(g)(1)(v), each man lock must have a clock, thermometer, and a continuous recording pressure gauge with a 4-hour graph installed outside the lock (changed prior to each shift's decompression) and a pressure gauge, clock, and thermometer inside the lock; copies of each graph must be submitted to the appointed physician after each shift.

• Keep charts legible, visible to the lock attendant, and retain copies per medical and record requirements.
• See 1926.803(g)(1)(v).

Under 1926.803(g)(1)(vi) and (vii), except where air pressure is below 12 p.s.i.g. and there is no danger of rapid flooding, all caissons with working area greater than 150 square feet and each bulkhead in tunnels 14 feet or more in diameter (or equivalent area) must have at least two locks in perfect working condition—one for men and one for materials; where only a combination lock is required, it must have capacity for two successive shifts.

• Ensure both locks are maintained and function separately as man and materials locks when required.
• See 1926.803(g)(1)(vi) and 1926.803(g)(1)(vii).

Under 1926.803(g)(1)(viii), emergency locks must be large enough to hold an entire heading shift and a limit maintained of 12 p.s.i.g.; there must also be a chamber available for oxygen decompression therapy to 28 p.s.i.g.

• Emergency locks must accommodate the full shift population and the facility must support oxygen therapy up to 28 p.s.i.g. as specified.
• See 1926.803(g)(1)(viii).

Under 1926.803(g)(1)(ix), the man lock must be large enough so occupants are not compelled to be in a cramped position, must have at least 5 feet of clear headroom at the center, and a minimum of 30 cubic feet of air space per occupant.

• Design man locks to meet these dimensional and volume requirements to ensure comfort and safety during compression and decompression.
• See 1926.803(g)(1)(ix).

Under 1926.803(g)(1)(x), locks on caissons must be located so that the bottom door is not less than 3 feet above the water level surrounding the caisson on the outside.

• This placement helps prevent water ingress and maintains lock safety and operation.
• See 1926.803(g)(1)(x).

You must keep an accurate pressure gauge on both the outer and inner sides of each bulkhead, in addition to the lock gauge, and make them accessible and working at all times. See the requirement in 1926.803(g)(1)(xi).

• Place gauges so attendants can read them at all times and check them frequently for accuracy.
• Keep gauges calibrated and repair or replace any that are not accurate.
• Maintain the lock gauge plus the two bulkhead gauges to provide independent verification of pressure on both sides of the bulkhead.

The man lock must have an observation port at least 4 inches in diameter located so all occupants can be seen from the working chamber and from the free-air side of the lock. This is set out in 1926.803(g)(1)(xii).

• Install the port where attendants and rescuers can observe occupants during pressure changes and emergencies.
• Ensure the port remains clear (not covered or painted over) and is included in routine inspections.

Man locks must have adequate ventilation so occupants have fresh air and no pockets of stale air. See 1926.803(g)(1)(xiii) and the general ventilation rules in 1926.803(i).

• Provide forced ventilation during decompression as required by 1926.803(i)(4).
• Design ventilating systems to avoid dead-air pockets; outlets along the supply line may be necessary (1926.803(i)(1)).
• Monitor air quality and keep records each shift per 1926.803(i)(2).

Man locks must be maintained at a minimum temperature of 70 °F. See 1926.803(g)(1)(xiv).

• Keep heating systems reliable and monitored so the temperature does not fall below 70 °F while employees occupy the lock.
• For working chambers (not locks), note that compressed-air working chambers must not exceed 85 °F unless additional controls are provided (1926.803(i)(3)).

You must provide a special decompression chamber whenever the total decompression time at the end of a shift exceeds 75 minutes, and that chamber must provide at least 50 cubic feet of airspace per employee and 4 square feet of free walking area plus 3 square feet of seating space per occupant. See 1926.803(g)(1)(xvii) and 1926.803(g)(2)(i).

• Post the chamber’s rated capacity at the entrance based on these minimum space requirements and do not exceed it except in an emergency.
• The chamber must allow occupants to sit without cramping; seating dimensions are specified in 1926.803(g)(2)(iii).

A special decompression chamber must have clocks, pressure gauges, valves to control air supply and discharge, valves and piping to control pressure from inside and outside, effective oral intercommunication with the attendant and the compressor, and an observation port at the entrance. See 1926.803(g)(2)(ii) and its subparagraphs (a)–(f) for details.

• Ensure attendants and occupants can read the clock(s) and pressure gauges easily (1926.803(g)(2)(ii)(a)–(b)).
• Maintain two-way voice communication between chamber occupants, the attendant, and the compressor plant (1926.803(g)(2)(ii)(e)).
• Keep valves and piping arranged so pressure can be controlled from both inside and without (1926.803(g)(2)(ii)(d)).

Special decompression chambers must provide seating that permits a normal sitting posture (at least 18 by 24 inches per occupant), adequate toilet and washing facilities (with toilet bowls that have a rim protector to create an air space when the lid is closed), fresh drinking water available, and the chamber must be kept clean with no accumulation of refuse. See 1926.803(g)(2)(iii)–(vi).

• Provide screened or enclosed toilet/washing recesses and maintain them sanitary (1926.803(g)(2)(iv)).
• Offer drinking water by piping, fountains, or individual canteens; do not use community drinking vessels (1926.803(g)(2) text).
• Keep records of cleaning and inspections as part of your site sanitation program; OSHA has explained employers’ sanitation obligations in a recent letter about sanitation applicability.

Unless the special decompression chamber serves as the man lock to atmospheric pressure, it should be situated adjacent to the man lock on the atmospheric pressure side, with a passageway that lets employees move from the man lock to the special chamber without reducing ambient pressure for the next decompression stage. See 1926.803(g)(2)(vii).

• Design the passageway so it does not interfere with normal man-lock operation or the release of occupants to atmospheric pressure after decompression.
• Where practical, place the chamber to minimize transfer distance and avoid unnecessary pressure changes during movement.

You must have a thoroughly experienced, competent, and reliable person (a gauge tender) on duty at the air control valves at all times to regulate pressure, and the compressor plant must have sufficient capacity, redundancy, and power arrangements to maintain safe working pressures and handle emergencies. See 1926.803(h)(1)–(9).

• One gauge tender may regulate pressure in up to two tunnel headings if gauges and controls are co-located; caisson work requires a gauge tender per caisson (1926.803(h) text).
• Low-air compressors must be sized with a margin for emergencies and repairs (1926.803(h)(2)).
• Provide at least two independent power sources for low-air units, each capable of operating the entire low-air plant (1926.803(h)(3)).
• Maintain duplicate low-pressure feedlines with one extending within 100 feet of the working face and install check valves on all air supply lines (1926.803(h)(6)–(7)).
• Low-pressure air must be regulated automatically, with manually operated valves for emergencies (1926.803(h)(8) and related text).

Ventilating air must be at least 30 cubic feet per minute and the employer must analyze workplace air no less than once each shift, keeping records of those tests; test results must meet the threshold limit values in subpart D and be within 10 percent of the lower explosive limit for flammable gases. See 1926.803(i)(1)–(2).

• Provide exhaust valves and pipes to eliminate dead-air pockets; use intermediate outlets along supply lines if needed (1926.803(i)(1)).
• Keep air-test records on file at the work location for inspection or review (1926.803(i)(2)).
• If tests show contaminant limits are exceeded, take immediate corrective action as required by 1926.803(i)(2).
• For guidance on employer hazard assessment and PPE selection where contaminants are present, see OSHA’s PPE hazard assessment letter.

Working chambers under pressure must be kept at temperatures not to exceed 85 °F by after-coolers or other suitable devices, forced ventilation must be provided during decompression, and positive means to remove heat buildup are required when using heat-producing machines. See 1926.803(i)(3)–(5).

• Use after-coolers, ventilation fans, or other engineering controls to maintain temperatures at or below 85 °F (1926.803(i)(3)).
• Provide forced ventilation during the entire decompression period, using chemical or mechanical purification as needed (1926.803(i)(4)).
• If tunnel machines (moles, shields) produce heat, install positive removal systems (exhaust/ventilation) at the heading (1926.803(i)(5)).

All lighting in compressed-air chambers must be electric only, with two independent lighting systems (an automatic emergency source), and minimum illumination of 10 foot-candles on walkways; electrical equipment and wiring must comply with Subpart K and nearby fixtures must be made of noncombustible, nonabsorptive insulation or grounded metal. See 1926.803(j)(1)–(6).

• Provide two independent lighting systems; the emergency system must come on automatically if the primary fails (1926.803(j)(1)).
• Maintain at least 10 foot-candles on any walkway, ladder, stairway, or working level (1926.803(j)(2)).
• Ensure portable lamps have insulating sockets, approved handles, guards, and cords (1926.803(j)(5)).
• Do not use worn or defective portable conductors (1926.803(j)(6)).

Employers must provide sanitary, heated, lighted, and ventilated dressing and drying rooms with benches and lockers, showers at a ratio of one to 10 employees per shift, and at least one toilet per 15 employees; all working compartments must be kept sanitary. See 1926.803(k)(1)–(3).

• Provide heated dressing/drying rooms and adequate lockers and benches (1926.803(k)(1)).
• Supply showers (1 per 10 employees per shift) and toilets (1 per 15 employees or fraction thereof) with running hot and cold water (1926.803(k)(1)).
• Keep caissons and working compartments sanitary (1926.803(k)(3)).
• For how OSHA applies sanitation standards across different workplaces, see OSHA’s sanitation applicability letter.

You must provide and maintain firefighting equipment (including fire hoses and appropriate extinguishers), have a firewatch during welding or flame-cutting, supply water lines and hose outlets where flammable materials exist, and avoid storing highly combustible materials in the working chamber. See 1926.803(l)(1)–(8).

• Keep firefighting equipment in working condition and have a firewatch with a hose or extinguisher during hot work (1926.803(l)(1)–(2)).
• Provide a 2-inch minimum waterline into the tunnel working chamber and within 100 feet of the working face with hose outlets and 100 feet of hose attached as specified (1926.803(l)(6)).
• Maintain at least two approved water-based extinguishers in the working chamber and avoid extinguishers that could harm occupants (1926.803(l)(7)).
• Do not store highly combustible materials in the working chamber (1926.803(l)(8)).

Man locks must have both an internal and externally-activatable fire-extinguishing capability, and combustible materials in compressor buildings or working chambers are limited to amounts that will not create a fire hazard. Specifically, 1926.803(l)(9) requires man locks to be equipped with a manual-type fire extinguisher system that can be activated from inside the man lock and by the outside attendant, and also requires a fire hose and a portable dry-chemical fire extinguisher inside and outside the man lock. The general provision in 1926.803 states that wood, paper, and similar combustible material shall not be used in the working chamber in quantities which could cause a fire hazard, and that the compressor building shall be constructed of non-combustible material.

• Required equipment in man locks: manual fire-extinguishing system operable from inside and outside, a fire hose, and a portable dry-chemical extinguisher (1926.803(l)(9)).
• Materials: avoid combustible materials in working chambers if they could create a fire hazard; compressor buildings must be noncombustible (1926.803).

Follow these requirements to ensure quick fire response and to minimize fire risk where compressed-air operations are being conducted.

You must install intermediate bulkheads and/or safety screens where rapid flooding is possible, provide elevated noncombustible walkways with railings in large tunnels, and test bulkheads used to contain compressed air to ensure they resist the maximum expected pressure. In detail, 1926.803(m)(1) requires intermediate bulkheads with locks or intermediate safety screens (or both) where there is danger of rapid flooding. For tunnels 16 feet or more in diameter, 1926.803(m)(2) requires hanging walkways from the face to the man lock placed as high as practicable with at least 6 feet of headroom, constructed of noncombustible material, and equipped with standard railings installed in accordance with Subpart M (1926). Finally, bulkheads used to contain compressed air should be tested, where practicable, to prove they can resist the highest air pressure expected to be used (1926.803(m)(3)).

• Bulkheads/safety screens: required where rapid flooding may occur (1926.803(m)(1)).
• Walkways (tunnels ≥16 ft): hanging, noncombustible, ≥6 ft headroom, skidproof ramps under screens, and standard railings per Subpart M (1926.803(m)(2)).
• Bulkhead testing: where practicable, test bulkheads to prove resistance to the highest expected air pressure (1926.803(m)(3)).

Complying with these provisions helps protect workers from flooding hazards and ensures safe egress and access in compressed-air tunnel operations.