Hi arm,
IAQ is relative. It gives an indication of the relative change in ambient TVOCs detected by BME680.
IAQ = 25 corresponds to typical good air and IAQ = 250 corresponds to typical polluted air.
In your use case you mentioned, IAQ value will drop from 400 to a lower value and spans from 25 to 250 after a long time in a stable environment, but it won't stay at 250.
... View more