I've been wondering about the meaning of the IAQ number and the raw resistance. It appears to me the BME680 gas sensor is a device that generally reacts to VOC's. I'm guessing the sensor is not stable (most likely the zero offset but not sure) and needs to be exposed to different environments to get a sense of high and low VOC exposure. If I'm correct a sensor exposed to a constant VOC environment would never leave the  accuracy. When I first got my sensor running I let it run for 3 to 4 days. I had not yet gotted the BSEC code working. When I got the BSEC code working (but no state saving) I performed the following: Ran the sensor for about 4 hour, still at accuracy . Put some alcohol on a paper towel (wet probably a 1 inch circle). Placed the paper towel ~ 6inches from the BME680. The IAQ spiked up and when it came back down (removel of the towel) the accuracy was  So it seems the IAQ algorithm takes what is generally expected from the VOC sensor, factors in the min and max VOC exposure and tries to create some calibration coefficients. For those who know more about this sensor than us mere mortals, is there a way to simulate some high and low VOC conditions (in the home) to accelerate the calibration procedure? And perhaps increase the accuracy. I was thinking about a near 100% helium for the "clean air" point. I thought about a container with 100% ethanol (sensor would be in the vapor, not liquid) but don't know off hand how to extimeat the concentration, and I'm concerned such a high VOC level might shift the sensor output and or damage the sensor. Having said all this, I realize the VOC sensor is what I would call a "ballpark" sensor, but I'm a curious fellow 🙂 and am interested what goes into the IAQ reading.
... View more