Sensirion SCD4x Carbon Dioxide (CO2) Gadget is a simple reference design circuit board that demonstrates the performance and ease of use of Sensirion’s SCD4x CO2 sensors. The SCD4x CO2 Gadget features an RGB LED, with the traffic light color scheme, indicates the indoor air quality based on the measured CO2 concentration. It also incorporates a BLUETOOTH® Low Energy module to communicate with BLUETOOTH® Low Energy (BLE) capable devices like smartphones. Power is supplied via a standard USB interface. The CO2 Gadget application runs with Android 4.4 or later and iOS 9.0 or later, respectively.