(a) Upon the premises on which explosives are stored there shall be posted signs with the words “EXPLOSIVES — KEEP OFF” legibly printed thereon in letters not less than 3 inches high. Signs shall be placed so that a bullet passing through them will not strike any nearby magazine.
(b) When explosives are being processed or are used in connection with any manufacturing process or if explosives are stored at such manufacturing establishment, a sign no smaller than 4 square feet bearing the words “DANGER — EXPLOSIVES” shall be kept posted at the main plant entrance and, in addition to this, the remainder of the premises shall be posted with signs as set forth in subsection (a) of this section.