The maintenance-free on-wall sensor AERASGARD® AFTM - LQ- CO2 - Modbus (max. expansion level) and ACO2/ ALQ - CO2/ AFTM - CO2 - Modbus with Modbus connection, automatic calibration, in an impact- resistant plastic housing with quick-locking screws, plastic sinter filter (replaceable), optionally with/without display, for determining the CO2-content of the air (0...5000 ppm), of the air quality (0…100 % VOC), the temperature (–35...+80 °C) and the relative air humidity (0…100 % RH). International system of units SI (default) can be changed to imperial (via Modbus). The following parameters can be accessed via the Modbus: Temperature, relative humidity, air quality (VOC), carbon dioxide (CO2) and atmospheric pressure. The sensor is used in offices, hotels, convention centres, apartments, shops, etc. for the purpose of evaluating the indoor climate. This enables energy-saving room ventilation on an as-needed basis, thereby reducing operating costs and improving well-being. One sensor for every 30 m²of space is recommended.