Unrealistic values for nitrogen dioxide from Grove multichannel gas sensor

Good morning,

My organisation purchased a Grove Multichannel Gas sensor from Digi-Key in the UK to measure pollution levels. We have been having problems with measuring nitrogen dioxide levels. The wiki page for this sensor says that the nitrogen dioxide level cannot go over 10ppm, but we have been regularly getting much higher values:

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The NO2 values being reported by the sensor are not realistic, especially considering that the air pollution is lower than usual at the moment due to the lockdown. As you can see from the graph showing the levels for a 24 hour period, it is also reporting that the levels increased dramatically overnight, whereas you would expect the opposite to be true.

The sensor was last calibrated in February, and it is currently up on the side of a building so it would be difficult to calibrate it again.

It is connected to an Arduino Pro Mini via I2C and being powered by 3.3v. It was programmed using the Arduino IDE and the library provided by Seeed.

We suspect that the sensor is faulty, or do you have any other idea why the nitrogen dioxide is so high?

Thank you!

Are you using this one?

No we are using version 1:

V1 does have some strange problems, the original chip factory suggested that we do not produce, I recommend you to use V2.

Oh ok then, thank you.