Calibration Confusion

[Mike]

I am looking at purchasing and am confused by the calibration instructions.

Monitor Calibration

This page states “For most applications, a single calibration before deployment is enough.” and “Without calibration, the sensors in the AirGradient monitor provide enough accuracy to give you an idea of the general pollution levels”. I only need general levels, this would be for home use, but these statements are implying that the sensors are NOT calibrated by default.

In contrast, on the product page it states that “Every sensor goes through a multi-step testing and calibration process to ensure the highest accuracy.” and that specifically the PMS5003 sensors are already factory calibrated.

Are the sensors calibrated or not? If they are already calibrated, wouldn’t my amateur calibration attempts “ruin” the factory calibration? I feel like I’m missing something.

[Altair_AirGradient]

Hi @Mike,

The reason the UNDP toolkit mentions “calibration before deployment” is because the toolkit is aimed at large scale research network deployment. When you deploy tens or hundreds of devices in the field and need all of them to align very closely with each other, researchers typically co-locate them near a reference station for a few days. That’s about tightening reproducibility across the whole fleet. For normal home use, this is not necessary.

Every PMS5003 already has its own factory calibration, and on top of that we run all monitors through an additional calibration process before they leave our workshop. With the introduction of Test Report Version 2, these calibration factors are now tied to the device’s serial number, so each unit gets its own correction layer to ensure reproducibility. For home use, you don’t need to calibrate anything. The device is ready out of the box.

[superjeng1]

Three more things I wanted to add/ask.

First, for custom formula, I should choose Custom via PM Count not Custom via PM2.5 Raw, is that correct? I assume this because I see “Calibration Parameters via Count” in the test report, please correct me if I am wrong.

Second, assuming we should use the value from the test report for the calibration page, if a user buys a fully assembled unit, I think the message asking the user to apply the calibration should not appear or should apply the value from the test report, do you agree?

Finally, I think the time in my notes were wrong, it should have been 8PM not 8AM.

[superjeng1]

Hi, I have just received a fully assembled Airgradient One. But I am confused by the PM2.5 Calibration Formula page in the advanced settings. I see PMS5003_20240826 was preselected, but the scaling factor and offset value is different than the one in my test report.

Then I found in the notes section, that the values in the test report was set but changed to PMS5003_20240826 minutes later. My guess would be that was when I clicked the apply calibration button from the banner message right after I set up my device.

id,title,description,date,measure,location_id,place_id
"32270","Calibration formula change","The calibration formula has changed, now slr_PMS5003_20240826 is applied","2025-12-04T08:38:01","pm02","178334","20263"
"32239","Calibration parameter change","The calibration parameters have changed, now offset -0.271 / scaling factor 0.014 epa false are used","2025-12-04T08:33:26","pm02","178334","20263"
"32238","Calibration parameter change","The calibration parameters have changed, now offset -0.271 / scaling factor 0.014 epa false are used","2025-12-04T08:33:26","pm02","178334","20263"
"32237","Calibration formula change","The calibration formula has changed, now custom is applied","2025-12-04T08:33:26","pm02","178334","20263"
"32236","Calibration formula change","The calibration formula has changed, now custom is applied","2025-12-04T08:33:26","pm02","178334","20263"

My assumption here is, I should manually enter the value in the test report, and not to check the EPA option?