California Code of Regulations
Title 8 - Industrial Relations
Division 1 - Department of Industrial Relations
Chapter 4 - Division of Industrial Safety
Subchapter 14 - Petroleum Safety Orders-Drilling and Production
Article 46 - Liquid Loading and Unloading Facilities and Operations
Section 6651 - Loading and Unloading Operations

(a) During the loading and unloading of flammable liquids into or from truck or trailer tanks, no repairs, adjustments, or other operations shall be performed upon a truck, truck engine, trailer, truck tank, or trailer tank.

(b) During the loading and unloading of a tank truck or trailer, the truck engine shall be stopped and the cab shall be unoccupied, unless the cargo is moved by means of the truck engine or an auxiliary engine with controls located in the cab, in which case the cab may be occupied by the truck operator.

(c) When a tank truck engine or an auxiliary internal combustion engine is being used to furnish power to transfer a flammable liquid, the vapors that may be liberated by such transfer shall be prevented from reaching the truck or auxiliary engine. If necessary, the vapors shall be piped to a safe location.

(d) During the loading and unloading of a tank truck or trailer, a qualified person shall be at or near the loading or unloading controls.

(e) In loading and unloading of tank cars, tank trucks or trailers, provision shall be made for the safe disposal of the liquids released by overflow or from hose spouts or lines.