Which PurpleAir parameters to use for EPA PM2.5 correction?

Data API
1

Hi All,
I was directed to read the EPA pdf that contained the correction equation for PM2.5 reading. I created the formula but not sure where to get in the PurpleAir API the needed data. For example for PM2.5 the equation is:
PM2.5=0.541PA_cf1(avgAB)-0.0618RH +0.00534*T +3.634

T or temperature I am assuming we use the the temperature reading from the API
PA_cf1(avgAB) What is that? Is it pm2.5_cf_1?
RH means relative humidity is that the humidity parameter in the API?

I am hoping to just make one API call to get these variables.
Any help appreciated!

2

What is your source for that formula? I’ll update the other thread.

3

Your questions are fine. I got the EPA from the AirNow map.
https://gispub.epa.gov/airnow/?monitors=pm25&contours=none&xmin=-14256862.295991126&xmax=-13214872.726407655&ymin=5865361.713785472&ymax=6342328.770284948

4

The formula I got from an EPA document. It was mentioned on another thread.

5

Here is the doc where I was sent to get the latest EPA formula.
https://cfpub.epa.gov/si/si_public_record_report.cfm?Lab=CEMM&dirEntryId=354999

6

In the EPA document you mentioned. The latest set of equations are:

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7

For 1-hour average data, EPA calculated it from rolling 10 minute average following their quality control procedure.

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8

Therefore, the PurpleAir parameters used in EPA PM2.5 correction are:

humidity : Relative humidity
pm2.5_10minute_a : channel A of rolling 10 minute average
pm2.5_10minute_b : channel B of rolling 10 minute average

Mare sure the location_type is 0 so it is an outdoor sensor. for outdoor sensors, pm2.5_10minute_a and pm2.5_10minute_b are cf_atm

From PurpleAir API web page (Loading...)

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9

@adanecito, Reason I was asking was that none of the EPA published formulas have a correction for temperature, but yours (the formula in the top post) does.

Man, EPA went off the deep end trying to reverse engineer CF_ATM.

10

I can agree with you. But that is the standard and I believe in standards. ugh.

11

There is an improved formula on API. The name is “PM2.5 alt”. The same formula is available for downloading on the PurpleAir mapping page, where it is called “ALT-CF3”. It is based on several published peer-reviewed papers referenced on the mapping page. It’s a good deal simpler than the latest EPA formula.