You are missing the point. The reason the graph looks like that is because the unit is producing readings of 30Meg to 50Meg for short periods of time – perhaps only 1 or 2 samples. Historically, the “sensible readings” have been in the range of 300K. The ratio of 30M to 300K is 100:1. According the specs the Winsen MP503, the range from quite polluted to quite clean is on the order of 10:1. So such big readings cannot be coming from a healthy sensor.

see the graph within this document https://www.winsen-sensor.com/d/files/ZP07-MP503.pdf

This sensor gives lower readings with more VOC. These >10Meg “spikes” would therefor represent sudden spikes of amazingly clean air amongst a background of almost continuous high pollution. This is nonsensical.

These very big readings of >>10M have only appeared in recent months (coinciding with colder weather) that is why I suspect it is the start of a failure. I see that the device has a small built-in heater, perhaps that is what is failing. I suppose time will tell.

Ken