The Milesight UC502-868M-EA is a compact, energy-efficient LoRaWAN sensor for comprehensive indoor air quality monitoring. It precisely measures carbon dioxide (CO2) concentrations, temperature, humidity, and volatile organic compounds (VOC), making it ideal for smart building applications in offices, schools, and public facilities. The integrated LoRaWAN communication in the 863–870 MHz frequency range (EU868) enables reliable wireless data transmission over long distances — up to 15 km in open field — ensuring stable connectivity with IoT platforms such as Milesight IoT Cloud, TTN, or Helium. Thanks to its energy-efficient technology and power supply via two replaceable 3.6 V ER14505 Li-SOCl2 batteries, the sensor achieves a battery life of up to 5 years, depending on measurement intervals and usage. The compact and discreet design, with dimensions of 90 × 90 × 35 mm and a weight of approximately 135 g, allows for unobtrusive wall or ceiling mounting using either adhesive or screw fixation. Configuration is simple via USB-C, NFC, or the ToolBox app, significantly simplifying deployment and maintenance. The CO2 measurement accuracy is ±(50 ppm +3 % of reading), ensuring reliable real-time data for optimizing ventilation, comfort, and energy efficiency. The sensor is designed for indoor use and complies with IP30 protection rating, safeguarding it against dust and light splashing water.