• The return value is 2 bytes wide unsigned nitrogen oxides concentration value, the unit is 1 (AQI, i.e. air quality index), the resolution is 1, and the range from 0 to 65,534, although useful range is 0-500. Value 0xFFFF (i.e. 65,535) specifies a sensor error.
• FRC 2-byte: FRC return value is the nitrogen oxides concentration value +4 (i.e. 0x0036 = 54 is value 50). Because of FRC predefined values the raw values from 0xFFFC to 0xFFFF (i.e. 65,532 to 65,535) cannot be passed.