As used herein, the following terms mean:

(1) Approved. In compliance with a subsisting resolution of approval adopted by the department of labor and industries, division of safety.

(2) Adequate. The term when applied to materials, devices, structures, methods and procedures is synonymous with effective, equal, equivalent, firm, necessary, proper, safe, secure, substantial, sufficient, suitable and shall denote such kind and quality as a reasonable and prudent man experienced in compressed air work would require in order to provide safe working conditions for himself in the performance of the work.

(3) Bulkhead. An upright partition in tunnels separating compartments; a structure or partition capable of resisting pressure and separating a high pressure compartment from a low pressure compartment.

(4) Caisson. A structure in or by means of which excavation in a predominantly vertical direction is carried is carried on by persons working in a compressed air environment.

(5) Compressed air worker. A person performing any work or duty in compressed air. This term does not include divers.

(6) Designated person. A person selected and directed by an employer to perform a specified task or duty.

(7) Director. The director of the department of labor and industries, state of Washington.

(8) Effective, equal, equivalent. See (2), "adequate."

(9) Firm. See (2), "adequate."

(10) Job. The site, buildings, equipment and operations proximately associated with the work in compressed air.

(11) Lock. A chamber designed to facilitate the passage of men, materials and equipment from one ambient air pressure to another ambient air pressure.

(a) Emergency lock. A lock chamber designed to hold and to permit the quick passage of an entire shift of compressed air workers.

(b) Man lock. A lock chamber through which only men pass.

(c) Materials lock. A lock chamber designed and used normally for the passage of materials and equipment.

(d) Medical lock. A special lock chamber in which men suffering from decompression illness are placed for medical attention and treatment. Also used as a facility for preemployment physical examinations.

(12) Necessary. See (2), "adequate."

(13) Owner. The person, real or corporate, for whom the construction is being done.

(14) Pressure.

(a) Absolute. Gage pressure plus one atmosphere; viz, at sea level with a gage pressure of 30 pounds per square inch, the absolute pressure is 30 + 14.7 = 44.7 pounds per square inch.

(b) Ambient. That which encompasses on all sides, surrounds. Usually taken as the gage pressure.

(c) Atmospheric. A pressure of one atmosphere at sea level; the pressure of air at sea level, used as a unit of measurement, equivalent to 14.7 pounds per square inch. One atmosphere of pressure is also zero pounds per square inch gage pressure.

(d) Gage. That pressure measured by gage and indicating the pressure in pounds per square inch exceeding one atmosphere.

(e) Normal. Atmospheric pressure of 14.7 pounds per square inch at sea level or zero gage pressure.

(f) Total. Total pressure is a pressure of one atmosphere plus gage pressure. See (14)(a), "absolute."

(15) Safe, secure. See (2), "adequate."

(16) Shaft. An excavation made from the surface of the ground the longer of axis of which forms an angle with the horizontal greater than twenty degrees.

(17) Shafting. An air and watertight enclosure built in the roof of a caisson and extended upward until above the ground or water level.

(18) Shall. The word "shall" is always mandatory.

(19) Substantial, sufficient, suitable. See (2), "adequate."

(20) Supervisor. The supervisor of safety, department of labor and industries, state of Washington.

(21) Tunnel. The underground excavation for a passageway including all shafts and other openings leading to or from such excavation, and all places, buildings and equipment used in connection therewith. Tunnels which are administered as distinct units constitute separate jobs.

(22) Working chamber. The space or compartment in which the excavating is being done in compressed air.