Carbon dioxide (CO2) poses a significant health hazard in homes, particularly during winter when traditional heating methods, such as wood burning, are prevalent. These methods often lead to elevated CO2 levels, increasing the risk of respiratory issues and even fatalities. To address this critical concern, we introduce a novel ventilation system designed to effectively regulate CO2 levels and ensure a safe indoor environment. The system comprises a CO2 sensor, a temperature sensor, a fan, a yellow light indicator, and an automatic window opener. It operates under two scenarios: Scenario 1: Mechanical ventilation only: The fan operates to circulate air within the room when CO2 levels reach a predetermined threshold and the outdoor temperature is less than 17°C. Scenario 2: Combined mechanical and natural ventilation: The fan operates, and the window automatically opens when CO2 levels reach the threshold and the outdoor temperature is higher than 17°C. A computational simulation was employed to realistically depict the system's operational concept. The simulation tracked both carbon dioxide (CO2) movement within the room and the system's response to predefined CO2 concentration thresholds established by European regulations. The simulations demonstrate the system's effectiveness in reducing CO2 levels to safe limits within a reasonable timeframe. The simulations also highlight the benefits of combined mechanical and natural ventilation in optimizing energy efficiency and maintaining comfortable indoor temperatures. The proposed ventilation system offers a promising solution to mitigate the health risks associated with elevated CO2 levels in homes, particularly during winter when traditional heating methods are employed. Its adaptability to varying CO2 concentrations and external temperatures ensures a safe and comfortable indoor environment.