In this work, we report the fabrication of sensors’ element for humidity or gases, prepared by in situ polymerization of aniline N‐propansulfonic acid using ammonium persulfate in acidic medium. The polymer is being used in the form of powder or deposited in multiple layers onto the PET film. Various techniques including Fourier Transform infrared (FTIR), ultraviolet‐–visible spectroscopy (UV–vis), X‐ray diffraction (XRD) and scanning electron microscopy (SEM) were employed to characterize the as‐prepared sensing materials. The film has been tested for humidity influence, where the significant variations in electrical characteristics were observed, suggesting its usefulness for humidity sensors. Also, for different organic and inorganic gases, a relatively low operating temperature and important sensitivity were observed that indicate its applicability as an active element for general gases sensors. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47743.