You will often see the VOC AQI perfectly aligned with Formaldehyde readings. I love it, since the two sensors are using very different tech for their operation.
Tonight the sensor is reading at the maximum again, 5000 ppb (or 5 parts per million). Maybe a different sensor which has a higher maximum could be found for a newer model?
Sadly, this is most likely a formaldehyde sensor failure. Your unit variant uses analogue connection to sensors, so there is little we can investigate here. Newer A3’s communicate with the formaldehyde sensor via a serial connection.
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