Breathing clean air is essential for human well-being, yet odour nuisance remains a persistent issue in wastewater treatment facilities. These facilities emit hazardous gases such as methane, ammonia and hydrogen sulphide (H2S), which pose severe health risks, including suffocation, loss of consciousness and even death at high concentrations. Additionally, odorous emissions can lead to legal and regulatory challenges when wastewater treatment plants are located near residential areas. To address these concerns, this study proposes the design and development of an activated carbon filtered (ACF) odour control system (OCS) using a coal-based grasp sulphone carbon media filter. IoT-based monitoring techniques were employed to assess real-time concentrations of hazardous gases, with H₂S levels recorded over three months showing peak concentrations of 20 ppm, daily averages of 6–10 ppm and weekly averages of 5–8 ppm. The implementation of the ACF OCS successfully reduced H2S emissions to nearly zero ppm, demonstrating its effectiveness. Scanning electron microscopy (SEM) analysis confirmed the adsorption of H₂S by revealing structural changes in the activated carbon, while X-ray diffraction (XRD) analysis indicated minor modifications to its amorphous structure due to interactions with adsorbed compounds. The results validate the efficiency of the ACF system in mitigating odour emissions, improving air quality, and reducing corrosion risks in wastewater treatment environments.