This fourth edition of Safe Operation of Vacuum Trucks in Petroleum Service provides information concerning the safe operation of vacuum trucks engaged in all aspects of handling flammable and combustible liquids, associated waste water, produced water, sour water, basic sediment and water (BS&W), caustics, spent acids, or other fluids stemming from petroleum operations, products, powders, and the hazard of dust explosions.This publication discusses the types of vacuum pumps and cargo tanks associated with vacuum truck operations, the common hazards associated with those vacuum truck operations, and representative safe work practices and precautions to help prevent accidents and injuries. Annex F provides brief descriptions of a variety of incidents involving vacuum trucks, including offloading into open areas. These may be useful in reviewing specific operating procedures or developing materials for safety meetings or pre-job briefings.The scope of this Recommended Practice (RP) includes the use of vacuum/pressure trucks, skids, portable tanks, and trailers (herein referred to as vacuum trucks) to remove flammable and combustible liquids from tanks and equipment and to clean up liquid hydrocarbon spills. The scope includes movement of liquid mixtures (such as "produced water", BS&W, or tank bottoms) that may contain sufficient hydrocarbon material to present comparable hazards.These safe practices also apply to the operation of portable vacuum tanks, skids, and trailers typically used in emergency flammable and combustible liquid spill cleanup activities. While not included in the specific scope of this standard, Annex E presents information related to pneumatic (air moving) trucks and hoppers, typically used in the petroleum industry for removal of dry materials such as catalysts, dusts, powders, or residue.