Background: Among the many hygiene problems of a large industrial city, one of the most important is the protection of the environment from pollution by emissions from motor vehicles and industrial enterprises. In the case of chemical pollution of the environment, very resistant and capable of bioaccumulating in large quantities chemicals - substances that have carcinogenic or mutagenic properties or have adverse effects, in particular on the reproductive, endocrine, immune and nervous systems - pose a particular threat to public health. The development of various sectors of the national economy (non-ferrous and ferrous metallurgy), chemical industry, production of synthetic fibers, pesticides and mineral fertilizers and thermal power plants and motor transport in cities is associated with the emission into the atmosphere of a bouquet of toxic substances containing gas, steam and aerosol mixtures of 1-4 classes of danger: hydrogen fluoride (Hf), ammonia (Am), formaldehyde (Fo), acetate lead (Al), dust (D), phenol (Ph-ol), sulphur dioxide (SD), nitrogen dioxide (ND), suspended solids (Ss). Therefore, the establishment of hygienic regulations only in the isolated intake of substances is insufficient. Objective: To experimentally determine the peculiarities of the biological response of the rat organism under simultaneous four-month permanent aerogenic exposure of bi-, tri-, tetrocomponent chemical mixtures and development of their permissible values in the atmospheric air. Methods: A chronic experiment was carried out on 375 male rats weighing 100-130 grams, which were divided into 6 series, with 1, 2, 3, 4 and 5 series having 4 groups and 6 series having 5 groups of 15 individuals each. For inhalation action in the experiment, 200-liter chambers were used, proposed by B.A. Kurlyandsky. Results: With round-the-clock inhalation inoculation of rats, both binary and three-, four-component complex mixtures in relatively high concentrations, the animals showed general toxic and gonadotoxic effects, which were expressed in functional changes of the CNS, liver and kidney function, reducing the nonspecific resistance of the animal body, changing the functional state of sperm and the ability of male rats to fertilize. The results of studying the biological effect of binary mixtures on the example of Hf + Am and Al + Ph-ol on the animal body were found that at the total intake of the biological effect of chemicals is characterized by the dependence of "concentration - effect" and there is an "increase in effect." Analysis of changes in biochemical, physiological, hematological, embryo and gonadotoxic indicators arising in the animal body indicates that Hf + Am and Al + Ph-ol at the combined intake in chronic experiments also have a general toxic effect, manifested in violation of the CNS, liver, blood, enzymes and functional state of sperm. The results of the study of the combined resorptive action of small concentrations of a combination of three and four chemicals on the example of phenol + formaldehyde + lead acetate, as well as combinations of lead acetate + formaldehyde + sulfur dioxide + ammonia indicate that the nature of the combined action of substances of these mixtures is shown by the effect of "total summation." Consequently, in the development of air protection measures, the concentrations of individual substances in a mixture of phenol + formaldehyde + lead acetate should not exceed 0.33 MPC of each ingredient separately and 0.25 MPC - in a mixture of lead acetate + formaldehyde + sulfur dioxide + ammonia Conclusions: The nature of the biological response of the body, the combined effects of bi-, tri-, and tetrocomponent chemical mixtures in a constant inhalation of animals depends on the number of components that make up the mixture, the physical and chemical properties of the ingredients, their aggregate state and hazard class. In this case, the nature of the combined action of binary and complex mixtures with 3 and 4 components at inhalation intake into the animal body is manifested by the type of "summation effect" or "partial summation." In the atmospheric air of binary and complex mixtures, each substance at the "summation effect" of 0.25 and 0.33 or incomplete summation should not exceed 0.61, 0.68, 0.61 and 0.46 MPC, respectively - at their solo action