The detection and monitoring of carbon dioxide (CO2) are critical for ensuring air quality, industrial safety, and environmental health. CO2 is a key greenhouse gas, and its accurate measurement is essential for regulatory compliance, health hazard prevention, and climate change mitigation. Non-Dispersive Infrared (NDIR) technology has emerged as a leading solution for CO2 sensing due to its high sensitivity, selectivity, and robustness. However, the performance of NDIR sensors can be influenced by environmental factors such as temperature, humidity, and gas composition, necessitating precise calibration in controlled laboratory environments. This study presents the comprehensive laboratory characterization of an advanced NDIR CO2 sensor, designed for compactness and integration into IoT applications. The sensor features a novel optical design with a gold-plated reflective surface and an optimized optical path, enabling high infrared absorption while maintaining a small form factor. A dedicated setup was developed at the ENEA gas sensor characterization laboratory, including a 15 L large volume test chamber (LVTC) with controlled air composition and environmental conditions. The calibration procedure involved baseline recording, sensor response testing with target gas, and desorption phase evaluation. Results demonstrate excellent sensitivity (30 ppm per lsb), rapid response time (within seconds), and linearity (correlation coefficient near 1). Temperature drift was minimal and correctable via firmware, while no significant humidity-induced drift was observed. These findings validate the sensor's suitability for real-world applications, highlighting the importance of laboratory characterization in optimizing sensor performance and ensuring reliable CO2 monitoring in diverse environments.