No person shall permit the storage of or keep for sale, within the limits of the city of Pinole, any gunpowder, giant or blasting powder in larger quantities than fifty pounds. All such powder must be kept in copper cases within six feet and at the right hand side of the front entrance to the building where the same is kept; provided, however, that this section shall not apply to loaded cartridges or shells or powder in shells. (Prior code § 89).