(1) Wherever, in caisson work in which compressed air is used, and the working chamber is less than 11 feet in length, and when such caissons are at any time suspended or hung while work is in progress so that the bottom of the excavation is more than 9 feet below the deck of the working chamber, you must erect a shield therein for the protection of the employees.

(2) You must subject shafts to a hydrostatic or airpressure test, at which pressure they must be tight. 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.

(3) Whenever a shaft is used, you must provide it, where space permits, with a safe, proper, and suitable staircase for its entire length, including landing platforms, not more than 20 feet apart. Where this is impracticable, you must install suitable ladders with landing platforms located about 20 feet apart to break the climb.

(4) You must provide all caissons, having a diameter or side greater than 10 feet with a man lock and shaft for the exclusive use of employees.

(5) In addition to the gauge in the locks, you must provide an accurate gauge on the outer and inner side of each bulkhead. These gauges must be accessible at all times and kept in accurate working order.

(6) In caisson operations where employees are exposed to compressed air working environments, you must comply with the requirements contained in WAC 296-155-745.