BME680 strange IAQ-Index in classroom

[sciencegirl]

Hello,

I used the BME680 with the calculation into the IAQ-Index in a classroom. At the same time I meassured the CO2 value with another sensor in the classroom. Afterwards I made an history chart, which I attached, with both values and everytime the windows had been opened the CO2 value drops and the IAQ-Index increases. Normaly the IAQ-Index should also drop, shouldn't it? Could the time filters and the algorithm in the BME680 be the reason for this strange behavoir? Or is there another reason? Is there anyway I can fix it?

Thanks alot in advance.

[BSTRobin]

Hi sciencegirl,

Did the sensor run for total about 4 hours from power on to end of test? How does the accruracy value of the BSEC output change?

[sciencegirl]

Hey,

it ran for several days. The accuracy value was on 3 calibrated the whole time. I also tried it at home and always when I opended the window the same thing happend. I'm using the sensor with the ESPHome software and the bsec library.

[BSTRobin]

Hi sciencegirl,

In the picture you provided by you, is it BSEC_OUTPUT_IAQ or BSEC_OUTPUT_STATIC_IAQ?

After opening the window, We are not sure whether the IAQ has become larger because of bad outside air. We recommend you place a BME688 outside the window, and when the window is opened, observe the CO2 and IAQ output of the BME688 inside and outside the window.