Hello, I was trying to pull sensor data for pm2.5 using the API. I noticed that there’s an option to apply US EPA conversion formula to the data directly in the data layer on the website. However, I did not find a corresponding field that returns such data with conversion applied in the API call. Is…

With the fields currently available via the API, you will need to manually apply the correction formula to the raw data. The correction formula from the US EPA can be found here: Sensor data cleaning and correction: Application on the AirNow Fire and Smoke Map | Science Inventory | US EPA . You’ll ne…

Hi Andrew, thank you for the quick reply! I have tried to do exact what you said myself but had small issues. Basically, after applying the equations manually, I get very similar, but not exactly the same corrected numbers from directly downloading data using the “US EPA” conversion on the map. I ha…

Happy to help, Karen! I should clarify that the CF=ATM formula should be used for outdoor sensors. If you are in need of the formula for indoor sensors (CF=1), I can provide that as well. Should I use pm2.5_atm (an average of pm2.5_atm_a and pm2.5_atm_b) as the “x” shown on the equations? Yes, t…

Thanks Andrew, this is helpful. However, I’m still having issue matching the manually adjusted numbers to the map data for the hourly PM2.5 raw readings. I think I followed all the correct steps: download hourly pm2.5_atm using API, apply the EPA equations on them based on different conditions; fo…

Hi @Karen_Wang , I just tested the formula and was able to match the data from the API to the data on the map. Ensure you are using the most updated correction formula: PM2.5 = 0.52*PAcf_1 - 0.086*RH + 5.75 My apologies, I wrote the incorrect formula. I was still able to match up the data. The cor…

Thank you both! I finally get it to work. Turns out the ordering of calculation matters. The small difference was a result of averaging A and B channel first and applying the formula. Applying the correction formula for each channel separately and taking an average at the last step solves the proble…

When I use the equation on page 26 of that document, it doesn’t result in the same converted value as the map shows. For example, this JSON response shows a pm2.5_10minute value of 5.6 and humidity value of 62 (*note that I’ve changed the sensor_index and name to protect my privacy) “fields” : [“se…

Hi @Tatian I’m not seeing any sensor under that sensor index. Is that the actual sensor index of the sensor or a placeholder? If you don’t want to share your sensor index on a public forum, you can send it to the moderators (which will get to me) or send an email to contact@purpleair.com .

Thanks for your response. Sorry, that’s a placeholder value. I’ll email you the actual sensor index.

Thanks for the email. I took a look at a couple of things that I thought could be causing the problem, but everything appears to be in order. I think the only issue you’re running into is that the final number in your calculation is a mass concentration value (µg/m^3) whereas the value you’re compar…

Is there a field that returns data with US EPA pm2.5 conversion formula applied?

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Is there a field that returns data with US EPA pm2.5 conversion formula applied?

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