Stoughton, MA – August 6th, 2022 – Particles Plus, Inc. tested the Amazon Indoor Air Quality monitor using a precision particle generator engineered to calibrate particle counters to the ISO 21501-4 calibration standard. The procedure we followed in order to accurately establish results was to split the output of the particle generator, with one branch going to a Particles Plus® Handheld 8306instrument and the other branch going to a box containing the mounted the Amazon Air Quality Monitor (see images below).
Particulates of various sizes were run through the system and simultaneously recorded. The data for these tests is shown below along with graphs for each of the various particle sizes.
The data shows that the Amazon Air Quality monitor consistently under-represents the PM2.5 figures. More worrisome is that the instrument does not track linearly. Instead, as the concentration increases the reported value decreases, tending toward zero.
It is not clear what’s going on within the sensor, but perhaps coincidence within the chamber is significantly limiting the maximum particle counts, or there is not significant time between particulates for the photodetector to recover, and therefor the baseline is shifting.
None of the above concentrations are outside of normal operating ranges. Such instruments should comfortably operate at concentrations well over 100 μg/m3 and if there is an upper limit for an instrument it should ideally saturate at an upper limit far above 1 or 2 μg/m3.