In Air Quality (with either the cheap sensors or the government published data) it is important to know about the Air Quality Indices (AQI) and PM concentrations. Those are very different things. The AQI differ very much per country, per period (1 hr, 3 hr or 24 hr averages) and in scales (6 divisions or 10 divisions with subdivisions). To make it even more complex, some countries did combine the fine dust (PM) AQIs with indices for SO2 and NO2. That is ignored here. These graphs only deal with Particulate Matter sensors. Please be aware that the scaling of the graphs is dynamic.

I made a post on the forum in which I will add some links to the sites for specific countries. You will have to study yourself (if you want).

Please be aware that these charts only give the abolute measurements of the PM concentrations as given by the sensors used. The AQI levels for the different countries have great variations and I will not go through the trouble to display those levels in the graphs for the normative country selected.

The graphs show the indicative AQI levels of the EU-CAQI standards (researchgate paper) (UK explication) for the 1 hr series.

These will show you reasonable short term danger levels although maybe not standardized in your country. 24 hr levels are considered irrelevant in the context of a personal station: you will be dead before this level reaches a level where help services are activated. If the 1 hr level shows an unhealthy level you better start running away (precautionary principle).

Yes, big differences in different countries. Therefore: study the documents and the danger levels in the matrix I supplied.