California Code of Regulations
Title 8 - Industrial Relations
Division 1 - Department of Industrial Relations
Chapter 4 - Division of Industrial Safety
Subchapter 7 - General Industry Safety Orders
Group 26 - Driving and Pressurized Worksite Operations
Article 154 - Pressurized Worksite Operations
Section 6090 - Air Locks

(a) Except in emergency, no employees employed in compressed air shall be permitted to pass from the working chamber to atmospheric pressure until after decompression, in accordance with Section 6085.

(b) The time of decompression shall be posted in each air lock.

(c) The lock attendant shall be under the direct supervision of the physician required by Section 6120 and stationed at the lock controls on the free air side during the period of compression and decompression. The lock attendant shall remain at the lock control station whenever there are employees in the working chamber or in the air lock.

(d) Except where air pressure in the working chamber is below 12 psig, each air lock shall be equipped with suitable automatic controls which automatically regulate decompressions. It shall also be equipped with manual controls to permit the lock attendant to override the automatic system in the event of an emergency.

(e) A manual control, which can be used in the event of an emergency, shall be placed inside the air lock.

(f) For each 8-hour shift, a record of employees employed under compressed air shall be kept by the lock attendant. This record shall show period of stay in the working chamber of each employee and the time taken for decompression.

(g) A clock, thermometer, and continuous recording pressure gauge with a 4-hour graph shall be installed outside of each air lock and shall be changed prior to each shift's decompression. The chart shall be of sufficient size to register a legible record of variations in pressure within the air lock and shall be visible to the lock attendant. A copy of each graph shall be submitted to the physician after each shift. In addition, a pressure gauge, clock, and thermometer shall also be installed in each air lock. Additional fittings shall be provided so that test gauges may be attached whenever necessary.

(h) Except where air pressure is below 12 psig and there is no danger of rapid flooding, all caissons having a working greater than 150 square feet and each bulkhead in tunnels of 14 feet or more in diameter, or equivalent area, shall have at least 2 locks in perfect working condition, 1 of which shall be used exclusively as an air lock. Where only a combination air and materials lock is required, this single lock shall be of sufficient capacity to hold the employees constituting two successive shifts. If emergency locks are provided, they shall be large enough to hold an entire heading shift and a limit maintained of 12 psig. There shall be a chamber available for oxygen decompression therapy to 28 psig.

(i) The air lock shall be large enough so that those using it are not compelled to be in a cramped position, and shall not have less than 5 feet clear head room at the center and a minimum of 30 cubic feet of air space per occupant.

(j) Locks on caissons shall be so located that the bottom door shall be not less than 3 feet above the water level surrounding the caisson on the outside. (Note: The water level, where it is affected by tides, is construed to mean high tide.)

(k) In addition to the pressure gauge in the locks, an accurate pressure gauge shall be maintained on the outer and inner side of each bulkhead. These gauges shall be accessible at all times and shall be kept in accurate working order.

(l) Air locks shall be illuminated and shall have an observation port at least 4 inches in diameter located in such a position that all occupants of the air lock may be observed from the working chamber and from the free air side of the lock.

(m) Air locks shall be maintained at a minimum temperature of 70 degrees Fahrenheit, dry bulb.

(n) When locks are not in use and employees are in the working chamber, lock doors shall be kept open to the working chamber, where practicable.

(o) All locks shall be constructed in accordance with the Unfired Pressure Vessel Safety Orders of the Division.

(p) Adequate ventilation shall be provided in accordance with Section 5143.