In this effective work, Polyethyleneimine (PEI) and Cerium Oxide (CeO₂) with disparate weight percentage were designated for sensing Carbon dioxide (CO₂). Four heterogeneous varieties of sensors with a varied weight percentage of CeO₂ in PEI were fabricated by drop-casting the sensitive films on prepared Interdigitated electrodes (IDE) from copper-clad. Morphological, compositional, absorbance and X-ray studies were led on the cerium oxide nanoparticles by field-emission scanning electron microscopy (FESEM), energy dispersive X-ray analysis (EDAX), UV-Visible spectrometer and X-ray diffractometer (XRD). Response capabilities of all the four sensors at room temperature were attentively scrutinized. Unique capabilities of Repeatability, sensitivity, error-free measurements of the response time and recovery time were carefully inspected. It was summarized that the appropriate weight ratio of CeO₂ and PEI was critical for sensing response. A feasible comparison between sensing responses of the fabricated sensors to CO₂ under nitrogen (N₂) was typically done. Relevant sensing process was investigated too.