Section 119.470 - Ventilation of spaces containing diesel fuel tanks(a) Unless provided with ventilation that complies with § 119.465 of this part, a space containing a diesel fuel tank and no machinery must meet one of the following requirements:(1) A space of 14 cubic meters (500 cubic feet) or more in volume must have a gooseneck vent of not less than 65 millimeters (2.5 inches) in diameter; or(2) A space of less than 14 cubic meters (500 cubic feet) in volume must have a gooseneck vent of not less than 40 millimeters (1.5 inches) in diameter.(b) Vent openings may not be located adjacent to possible sources of vapor ignition.