Update AQI breakpoints to 2024 values

[MallocArray]

#207

Update breakpoints to follow EPA guidelines from 2024

Also correct the formula to follow what is published on Wikipedia which changes a few values by 1 or 0.1 to match the existing breakpoints, such as Index low previously being 50 when the link shows it should be 51

https://www.epa.gov/system/files/documents/2024-02/pm-naaqs-air-quality-index-fact-sheet.pdf
https://en.wikipedia.org/wiki/Air_quality_index#Computing_the_AQI

[airgradienthq]

@MallocArray Thank you for contributing this. We will merge it in parallel of the adjustments we will need to do on the AirGradient dashboard side.

[airgradienthq]

@MallocArray is there a reason why you have the upper limit capped at 325 ug/m3?
The PMS sensor delivers data up to 500. Shouldn't we increase that number?

else if (pm02 <= 325.4)

[MallocArray]

It is based on the EPA formula found here:
https://en.wikipedia.org/wiki/Air_quality_index#Computing_the_AQI

They changed the breakpoints for the categories of AQI, and the highest PM2.5 range is 325 which will still calculate an AQI up to 500. If the PM2.5 was reported to be higher, it should no longer run through the formula, but report the max AQI value of 500
https://www.epa.gov/system/files/documents/2024-02/pm-naaqs-air-quality-index-fact-sheet.pdf

[airgradienthq]

There is the term "beyond index" by the EPA see for example:
https://2009-2017.state.gov/m/pri/gdi/airquality/c70218.htm

Also here it seems the newer version does not have the 500 as upper cap anymore:

https://www.epa.gov/system/files/documents/2024-02/pm-naaqs-air-quality-index-fact-sheet.pdf

I would recommend that we do not cap at 500.

[MallocArray]

Thank you for the links. It also brought me to the AirNow calculator which also does not cap at 500.
https://www.airnow.gov/aqi/aqi-calculator-concentration/

I'll revise the PR to no longer have an upper limit

[samuelbles07]

We will merge and make the change to accept values higher more than 500