It was shown for the first time that inhaling negative air ions (NAI) leads to changes in the functional state of the rat trachea mucosa, which in turn affects the phagocytic activity of blood cells. The effect depends on the concentration of the NAI, the duration of their action, and the sources of the NAI generation. For air ionization, technical ionizers and a bioionizer (a plant electrified through soil) developed by the Diod Company, Moscow, Russia were used. It was shown that the NAI at high doses (600 000 ion/cm3), generated by an Elion 131M device, induce a damage to the rat trachea mucosa, an inhibition of the activity of its antioxidant enzymes, and a decrease in the phagocytic activity of whole blood cells. Low doses of the NAI from the same source (25 000-50 000 ion/cm3) and high doses of the NAI from devices Elion 132S and 132R (320 000-500 000 ion/cm3), and a bioionizer (500 000 ion/cm3) produced a milder effect, activating the secretion of goblet cells of the trachea mucosa without its damage. A possible mechanism of the effect of inhaled NAI as exogenous reactive oxygen species (ROS) on internal processes in the organism is discussed. The involvement of the ROS in the action of ionized air found in the study is probably the general property of different electrical influences on biological objects. Therefore, the result of the investigation may be of interest for a wide circle of specialists dealing with ElectroMed influences