Piping systems shall comply with ANSI B31.3, Chemical Plant and Petroleum Refinery Piping. The additional provisions of this subchapter apply only to pressurized piping systems and components for LNG, flammable refrigerants, flammable liquids, and flammable gases, and unpressurized or low pressure piping systems, including vent lines and drain lines which handle LNG, flammable refrigerants, flammable liquids, and flammable gases with service temperatures below -20 degrees Fahrenheit.