This paper presents the development and implementation of an air quality monitoring system designed for integration into smart buildings using IoT technologies and low-cost hardware platforms such as Arduino. The system can measure critical pollutants such as carbon dioxide ( \(\text {CO}_{2}\) ) and carbon monoxide (CO) and additional environmental variables such as temperature and humidity in real time. A series of stress tests were carried out to assess the accuracy and reliability of the sensors. This showed that the system can detect dangerous levels of pollutants and provide early warnings via an intuitive graphical user interface. In addition, the web platform developed allows users to monitor and manage air quality data in real time, facilitating informed decision-making. The system is suitable for residential environments and has high potential for applications in public and commercial spaces, significantly contributing to improving environmental health and safety.