MIX8410 reads oxygen level as 30%

Hello, I am having trouble getting the Grove O2 sensor to provide accurate oxygen readings. I used the exact Arduino code provided here: Grove - Gas O₂ Sensor(MIX8410) - Seeed Wiki and applied 3.3V as they did in the example and I’m getting an oxygen reading of roughly 30%. I know atmospheric oxygen is supposed to be around 21%. Does anyone know what could be going on?

It need about 20~30 minutes to preheat the sensor, or you will get a larger value.

I don’t think that’s it. Even after a few hours of operation it was still reading at 30%

The sensor value only reflects the approximated trend of gas concentration in a permissible error range, it DOES NOT represent the exact gas concentration. The detection of certain components in the air usually requires a more precise and costly instrument, which can not be done with a single gas sensor. If your projects aim to obtain the gas concentration at a very precise level, then we do not recommend this gas sensor.