A. An opening galvanized iron vent pipe arranged for proper draining, or an automatically operated vent shall be provided for every tank which may contain flammable vapor. The lower end of the vent pipe shall not extend through the lip into the tank for a distance of more than one inch (1").
B. Vent openings for class I and II liquids, and vent openings or vent pipes exceeding two inches (2") for class III liquids shall be provided with approved flame arrestors and shall be of sufficient area to permit escape of air or vapor during the filling operation. Vent openings, except those automatically operated shall not be less than one inch (1") in diameter. Arrestors shall be accessible for examination and repair. Vent pipes shall be provided with weatherproof hoods and terminate outside of buildings twelve feet (12') above top of pipefill; or, if tight connection is made in filling line, to a point one foot (1') above the level of the top of the highest reservoir from which the tanks may be filled, and if possible, not less than three feet (3'), measured horizontally and vertically, from any window or other building openings. Where a power pump is used in filling storage tanks and a tight connection is made to the fill pipe, the vent pipe shall be no smaller than the fill pipe. (1961 Code)