Different PM readings

Hi, I have 3x ONE V9. The first one was from January 24 and was fully assembled; the other two were purchased as kits and arrived today. All run 3.1.3.

The old one (assembled) shows slightly higher PM1/2.5/10 readings and a much higher PM0.1 count (see the attached screenshot). First, they were in the same room, then I put them outside next to each other to calibrate CO2 and took the attached screenshot.

When they were indoors, and I blasted our air purifier to the max, all µg/m3 PMs went to zero after a few minutes, but PM0.1 counts were around 150 on the new ones and 400+ on the old one.

Is this normal? Do I have different sensors, or is the assembled one somehow calibrated? All the other sensors show identical readings.


Our understanding from the manufacturer is that the pm0.3 count are uncalibrated numbers whereas the ug/m3 figures are factory calibrated.

So the count numbers should not be compared between different sensor modules.

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Got it, thank you for the quick response.