Hi Anika from AirGradient here (the one who wrote the article).
Unfortunatly, we still depend on reference instruments to figure out the performance of a sensor. But you can find reference stations that publish their air quality data online.
If you want to do you own reference experiment, check if you can find a closeby air quality station and compare your data with this one. But keep in mind that, if reference and monitor are a few (kilo)meters apart, the air pollution emissions in the surroundings will probably differ. So you might not be able to compare every peak and squiggle, but I would expect that you can see a general correlation if you compare a sufficient time period (at least a week).
Unfortunatly, we still depend on reference instruments to figure out the performance of a sensor. But you can find reference stations that publish their air quality data online. If you want to do you own reference experiment, check if you can find a closeby air quality station and compare your data with this one. But keep in mind that, if reference and monitor are a few (kilo)meters apart, the air pollution emissions in the surroundings will probably differ. So you might not be able to compare every peak and squiggle, but I would expect that you can see a general correlation if you compare a sufficient time period (at least a week).