Air quality kit

Hi guys,
i’ve just installed the “air quality kit” and i have these results:

{
 "Event":"env-vals",
 "DeviceID":"e00fce6828c84e282644e681",
 "Data":"{\"temp\":29,\"humidity\":50,\"pressure\":1002,\"air-quality\":\"Low Pollution\",\"dust-lpo\":172522,\"dust-ratio\":0.575073,\"dust-concentration\":298.610657}",
 "Time":"2020-08-23 18:18::39+0200",
 "TTL":60
}

Only one question, there is a grade or scale for the dust lpo, dust ratio and dust concentration reccomended for a fresh air and not polluted? Where can i find it? Any advice?

Thanks

The value returned by the dust sensor is not well documented. The best reference is the Seeed Studio Page for it, but it still doesn’t say what reasonable values are, though there are some graphs.

The sensor itself is a Shinyei PPD42NS but the manufacturer’s page has even less information than the Seeed Studio page.