I was poking aroung on WXForum and noticed a message about changed breakpoints for AQI calculations. I am attaching the EPA pdf. pm-naaqs-air-quality-index-fact-sheet.zip (194.8 KB)
I know i don’t understand this stuff well, but it appears to me that AQI is estimated by taking the ratio of micrograms reading off the AQ sensor and extrapolating an AQI between the breakpoints. According to the EPA, its not really a calculation, but a lookup done here: [AQI Calculator Concentration | AirNow.gov](https://EPA Calculator)
Changing the array found in AQ_shared.php at line 43 appears to result in numbers now in conformity with the new breakpoints. But like i say, i don’t really know what i am doing.
Good luck, YMMV.
The original EPA is also heavily used outside the USA and it has become a “standard” in a lot of countries.
AFAICS there are no other users of the new “fine dust” levels → AQI tables.
So this is a difficult to solve problem for now.
If one moves to the new table and one will get in some cases a higher AQI value.
But that is not comparable anymore with other websites.
Being both well west of the prime meridian and well north of the equator, i prefer to be on the national standard, even if not adopted world-wide. I am unaware of any other websites close enough to me to make any comparisions. Most of the stations near me have no AQI and can’t figure out how to calibrate a barometer or a rain guage.