On the written permission of the chief of the fire department of the city, it is lawful for any person to keep or store any of the articles mentioned in Section 8.36.010 in quantities of not more than two hundred fifty gallons, in a one story brick or cement warehouse detached twenty feet from any other building, which warehouse building shall be used only for such storage and shall have a vent pipe not less than one inch in diameter extending at least six feet above the roof. Quantities in excess of fifty-five gallons may be kept or stored in tanks of iron or steel having a thickness of not less than three-sixteenths of an inch, such tanks to be placed outside the foundation of any building, the top of same to be at least two feet below the surface of the earth and to be completely covered by at least two feet of earth; each tank to be supplied with proper feed pipes and pump, and each pump to be equipped with an automatic cutoff. Such tanks shall be filled through a section of hose suitable for the purpose, which shall be detached from the feed pipe when not in service and the feed pipe securely closed. Gravity process for taking any of the articles from tank will not be permitted, and no such tank shall be located within twenty feet from any furnace, stove or fire.