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    BME688 BSEC IAQ need calibration

    New Poster

    BME688 BSEC IAQ need calibration


    I'm trying to use a BME688 sensor with the BSECv2 lib. 

    Everything seems to work ok except the IAQ, CO2, BreathVOC, etc. The accuracy is 0 when I start my program, then changes to 1 after ~5 minutes. According to the datasheet, 1 means it needs a calibration. I tried to close the sensor in a box with "bad" air for ~30mins, then take it outside for ~30mins. But the accuracy doesn't want to change. Also keep getting 25 for IAQ and 500 for CO2 equivalent.

    What could cause my problem?

    Thanks for the help!

    5 REPLIES 5
    Community Moderator

    Re: BME688 BSEC IAQ need calibration

    Hello ErvinBalazs, 


    I'm not sure which power mode you are using, but the IAQ value should be changed once IAQ accuracy reaches to 3. 

    CO2, BreathVOC as well. 

    It would be reached to value 3 in fast if BME688 is exposed to the various environment. 

    In your case, please put in "bad" air and "clean"air for 20~ 30 min. 


    New Poster

    Re: BME688 BSEC IAQ need calibration

    I already tried to put it into "bad" air and "good" air for 20-30 mins. But nothing changed.

    Could that cause the issue if the device restarted between the exposures?

    Also, do I need to do this every system start? Or it keeps it's calibration?

    New Poster

    Re: BME688 BSEC IAQ need calibration

    I am also experiencing these same issues with my BME688 setup using an ESP8266. Everytime I restart my board or swap configuration profiles I have to go through the five minutes of calibration in which my IAQ is stuck at 0 and then gradually goes to 1 and 2. Sometimes my IAQ never changes from 1 and other times it consistently remains at 2 and then transitions to 3 once I have introduced gas to the environment.

    I have burned my two breakout board sensors in for more than three days so I don't get why the calibration takes so long at startup. I don't have to wait at all for claibration with my Dev Kit, so I am wondering what is going on. @BST, Is there any way to start the sensor already calibrated (with an IAQ of 2-3) from the state file?

    Established Member

    Re: BME688 BSEC IAQ need calibration

    In normal case the BME680 sensor need a calibration time of some hours - if the environment have changed conditions.
    If not - it can take 3 days (in my case for a home office room) until it will reach iaqAccuracy 3.

    But after some time it can go back to "1" (not clear why in this time - see

    In any case you should save the sensor state - there is a sample in code. If not, the sensor will start at new with calibration when restarting the sketch.