I suspect that if you keep it away from the purifier, and closer to where you sit in the room, it's a more real representation of the air quality. Usually the air around the purifier would be purer than other parts of the room until an equilibrium has reached.
I haven't done extensive testing to validate this theory either, just a hunch. Let me know if my hunch is incorrect.
Right now the air quality sensor is in the basement, and the purifiers I'm comparing it to are upstairs. It's not a fair comparison, it just "seems" to be reporting using a different scale.
My plan is to put the sensor near one of my STARKVINDs and see how the numbers compare. This will tell me if they're measuring the same thing and reporting it at the same scale. Once I understand what the sensor is telling me a bit better, I'll put it in a more useful place. Your suggestion of putting it closer to where you sit is a very good one.
Humidity has a huge effect on the non-lab-grade sensors and that, combined with the fact that upstairs will have all the dander, fabric fibers, etc...of course they're different values.
I suspect that if you keep it away from the purifier, and closer to where you sit in the room, it's a more real representation of the air quality. Usually the air around the purifier would be purer than other parts of the room until an equilibrium has reached.
I haven't done extensive testing to validate this theory either, just a hunch. Let me know if my hunch is incorrect.