The rooms of the slaughterhouses shall be kept free of flies, roaches, rodents and other vermin. The use of poisons for any purpose in rooms or compartments where any unpacked meat or meat products are handled shall be permitted only under supervision of the director. (Mont. Co. Code 1965, § 101-17; 1972 L.M.C., ch. 16, § 13; 1980 L.M.C., ch. 38, § 1.)