When first connected to a Swidget wiring device, the Air Quality Insert will report a value of 25 and will not respond to changes in air quality until it has finished calibrating. This takes about 30 minutes, at which point it will begin reporting changes in your indoor air quality.
The reason this happens is that it takes some time to sample the air and calculate the air quality index. The sensor needs to recalibrate each time it is powered on. This includes when the Insert is removed and re-inserted into a Host, or when the power is reconnected to the host Device.