The Air layer
Air draws one dot per reading, colored by PM2.5, PM10, the VOC index, or the NOx index.
Air in the layer list is on by default. It draws one dot per Atmotube reading, at the place it was taken.
Under the Air box, pick the measure: PM2.5 by default, PM10, VOC index, or NOx index. That pick is not saved. An empty dot is a reading that had no such value. The pointer on a dot gives the value and the time.
The legend
With Air checked, a second legend gives the six colors of the chosen measure and their thresholds.
For PM2.5 and PM10 they are the guideline level and the four interim targets of the WHO global air quality guidelines (2021) for the 24-hour mean. PM2.5: 15, 25, 37.5, 50, 75 µg/m³. PM10: 45, 50, 75, 100, 150 µg/m³. A spot reading is not a daily mean. The color places the value. It does not judge it.
For the VOC and NOx indices, which run from 1 to 500, the first threshold is the average of the past 24 hours as Sensirion defines it: 100 for VOC, 1 for NOx. The next steps are display steps, not health thresholds. The source is named under the legend.
The same readings appear on the square's card in 3D, and on the fiche under Scan status. A reading deleted after the date you are looking at is still shown then.