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 13 - Cranes and Other Hoisting Equipment
Article 93 - Boom-Type Mobile Cranes
Section 4925 - Operator's Cab

(a) Operators exposed to the hazard of falling material or objects shall be protected by a canopy-type guard or cab over their usual operating position on the equipment except when such enclosure would interfere with the safe operation of the crane or create an additional hazard by excessively restricting the operator's vision.

(b) All windows on such equipment shall be safety glass, or equivalent, without optical distortion and possess optical qualities meeting standards of the California Department of Motor Vehicles. Wire glass, or equivalent, shall only be used for those windows through which the operator is not required to view the operations. Visibility forward shall include a vertical range adequate to cover the boom point at all times. The front window may have a section which may be readily removed or held open if desired. If the section is of the type held in the open position, it shall be secured to prevent closure.

(c) Exhaust gas discharge shall be away from the normal position of the operator. All exhaust pipes shall be guarded or insulated in areas where contact by employees is possible in the performance of normal duties.