The study of diluted solid solutions SrFe _x Ti _1-x O _3-δ (0.01 < x < 0.10). High-temperature X-ray powder diffraction (HTXRD), Mössbauer spectra and magnetic susceptibility measurements proved that up to x = 0.015 in the solid solutions there are clusters of Fe(III) atoms, which take part in ferromagnetic exchange through oxygen vacancy starting from 200 K via F-centers and a small fraction of single Fe(IV) atoms. An increase in iron content results in the larger clusters with ferromagnetic exchange both between Fe(III)-[O]-Fe(III) and Fe(III)-O-Fe(IV). The solid solutions are mixed electron-hole-ionic conductors and may be used as sensors of the humidity of gases.