The owner or operator in charge of any structure which on the effective date of this Act is being used for the storage of grain in bulk and which has a capacity of 10,000 bushels or more and the owner and operator in charge of any structure for storage of grain in bulk having a capacity of 1,000 bushels or more which is constructed or erected after the effective date of this Act shall have affixed to such structure or printed thereon a warning sign as required by this Act.
     The warning sign shall be affixed to or printed on the structure near the door or loading area and shall be substantially as follows:

    Inspect storage area for unauthorized persons before removing grain.”