Compare community sensors with official sensors
It is difficult to compare measurements of different sensors on simple values or points especially through raw measurements. The fact you find a factor 3 between the mentioned sensors is not surprising to me (it could also be sometimes more). However if you applied the right treatment of the data over a longer period you will realize that we can get an acceptable correlation between the official sensors and the community sensors; it is then useful for the community to rely on our SDS sensors to assess the evolution of the air quality where no official sensors are deployed.
To be better convinced by this philosophy you can refer to the post mentioned in reference where I specifically assessed the environment in Ulm based on the present sensors.
You could also check the methodology through the web site: https://www.deciphair.com