Caisson work safety requirements

Under 1926.801(a), a shield must be erected when the working chamber is less than 11 feet long and the caisson is at any time suspended so that the bottom of the excavation is more than 9 feet below the deck of the working chamber. See Requirement in 1926.801(a).

• Both conditions are required together: (1) working chamber length < 11 feet, and (2) suspension causing bottom > 9 feet below the deck. If either condition is not met, this particular shield requirement under 1926.801(a) does not apply.

Under 1926.801(b), shafts must be subjected to a hydrostatic or air-pressure test and be tight at the test pressure, and the shaft must be stamped on the outside shell about 12 inches from each flange to show the pressure to which it was subjected. See Requirement in 1926.801(b).

• The test may be hydrostatic or pneumatic (air-pressure) as specified.
• The stamping provides a visible record of the test pressure for inspectors and users.

Under 1926.801(c), whenever a shaft is used it must be provided, where space permits, with a safe, proper, and suitable staircase for its entire length including landing platforms not more than 20 feet apart; where a staircase is impracticable, suitable ladders shall be installed with landing platforms located about 20 feet apart to break the climb. See Requirement in 1926.801(c).

• Use a continuous staircase with landings ≤ 20 feet apart when space allows.
• If a staircase can’t be used, provide ladders with landings about every 20 feet to reduce long climbs.

Under 1926.801(d), any caisson that has a diameter or side greater than 10 feet must be provided with a man lock and a shaft for the exclusive use of employees. See Requirement in 1926.801(d).

• This is a mandatory requirement based on caisson size (> 10 feet).
• The purpose is to provide safe controlled access and egress for workers; employers must provide these features when the caisson meets the size threshold.

Under 1926.801(e), in addition to the gauge in the locks, an accurate gauge must be maintained on the outer and inner side of each bulkhead; those gauges must be accessible at all times and kept in accurate working order. See Requirement in 1926.801(e).

• Lock gauges alone are not sufficient—separate accurate gauges are required on both sides of each bulkhead.
• The gauges must be accessible whenever work is in progress and must be maintained to remain accurate.

Under 1926.801(f), when employees are exposed to compressed-air working environments in caisson operations, the employer must comply with the requirements in 1926.803. See Requirement in 1926.801(f).

• 1926.803 contains the specific safety, medical, and operational rules for compressed-air (hyperbaric) caisson work, so follow that section in addition to the provisions in 1926.801.

Under 1926.801(a), a shield is required only when the working chamber is less than 11 feet in length; therefore a chamber that is exactly 11 feet long does not meet that “less than 11 feet” condition and 1926.801(a) would not require a shield on that basis. See Requirement in 1926.801(a).

• Remember that both conditions in 1926.801(a) must be met (length < 11 ft and suspended with bottom > 9 ft below deck) for the shield requirement to apply.

Under 1926.801(a), the shield requirement is triggered when the bottom of the excavation is more than 9 feet below the deck; if the depth is exactly 9 feet, that does not meet the “more than 9 feet” criterion and 1926.801(a) would not require a shield on that basis. See Requirement in 1926.801(a).

• Both the depth and the working-chamber length thresholds must be satisfied together for the provision to apply.

No. Under 1926.801(e), in addition to the gauge in the locks, a separate accurate gauge must be maintained on the outer and inner side of each bulkhead—so lock gauges alone are not sufficient. See Requirement in 1926.801(e).

• Those outer and inner bulkhead gauges must be accessible at all times and kept in accurate working order to ensure correct pressure monitoring.

Under 1926.801(c), if a staircase is impracticable because of space limitations, suitable ladders must be installed and landing platforms located about 20 feet apart to break the climb. See Requirement in 1926.801(c).

• The intent is to provide safe, practical vertical access with platforms at regular intervals (≈ every 20 feet) even when a staircase cannot be used.

Under 1926.801(d), a man lock and shaft must be provided for exclusive employee use in caissons with diameter or side greater than 10 feet to provide controlled, safe access and to support compressed-air operations and worker decompression procedures. See Requirement in 1926.801(d) and follow-up requirements in 1926.803 for compressed-air work.

• A man lock functions as an air lock for safe entry/exit when pressure differences or decompression procedures are needed; providing it exclusively for employees reduces exposure and improves safety during compressed-air operations.

Under 1926.801(e), the employer must ensure that accurate gauges are maintained on the outer and inner sides of each bulkhead, that they remain in accurate working order, and are accessible at all times during operations. See Requirement in 1926.801(e).

• While 1926.801(e) does not use the word "employer" explicitly in that sentence, OSHA standards put the duty to comply on the employer; maintaining instruments and access is an employer responsibility under the OSH Act and related construction rules.

If caisson operations expose workers to compressed-air environments, the detailed safety and medical rules are found in 1926.803, and compliance with that section is required by 1926.801(f).

• Follow 1926.803 for requirements such as decompression protocols, medical surveillance, and other compressed-air protections that supplement 1926.801.

Yes. Under 1926.801(b), shafts must be tight at the pressure used during the hydrostatic or air-pressure test, and the shaft must be stamped on the outside shell about 12 inches from each flange to show the pressure to which they have been subjected. See Requirement in 1926.801(b).

• The stamping gives a clear record of the tested pressure; employers should retain any additional test documentation in accordance with good practice and inspection requirements.

Under 1926.801(c), landing platforms must be located not more than 20 feet apart when a staircase is provided and about 20 feet apart to break the climb when ladders are used in place of a staircase. See Requirement in 1926.801(c).

• The standard intends consistent rest points roughly every 20 feet for safe ascent and descent inside shafts.

The protections in 1926.801(a)–(f) set specific requirements for caisson work, but where employees are exposed to compressed-air environments 1926.801(f) explicitly requires compliance with 1926.803, and other applicable provisions of Part 1926 (e.g., general construction safety requirements) may also apply. See 1926.801(f) and Part 1926 overview.

• Employers should review 1926.803 for compressed-air specifics and the broader Part 1926 for related construction safety rules that may apply to caisson operations.