The research demonstrates that perovskite methylammonium lead iodide (MAPI) can detect various hazardous and polluting chemicals, including ammonia gas (NH₃), in the environment. To enhance the sensitivity and response time and modify the structural properties of pure MAPI, zinc sulfide (ZnS) is incorporated in three different concentrations (1, 2.5, and 5 wt%). The sensitivity of these ZnS-doped samples is evaluated for detecting NH₃ and alcohol vapor. Sensors based on MAPI:ZnS composites are fabricated on writing paper samples using a solution-processing technique. Upon exposure to NH₃, MAPI undergoes a colorimetric change from black to yellow. This phenomenon is attributed to the degradation of perovskite (MAPI) halides into lead (Pb) halides through the preferential adsorption of NH₃ molecules. The structural properties were analyzed using X-ray diffraction (XRD) patterns, which revealed a slight shift in the diffraction peaks towards higher 2θ angles. Field Emission Scanning Electron Microscopy (FESEM) images displayed rod-like morphologies, with an average diameter of approximately 49 nm for pure MAPI and around 46 nm for the ZnS-doped samples.