Questions about Wave Plus Room Air Sensor

I have been using the unit horizontally for over a year. I haven't read that the device should be hung on the wall. I have always received measured values. I can't prove whether the values are correct because I don't have another measuring device to compare them with.

No, of course not. Americium is also no longer used in new smoke detectors. The device works perfectly, by the way. If you are concerned about radioactivity, it is really worth measuring the radon concentration. It is the biggest exposure an average Swiss is exposed to and it varies quite a lot. I would buy the device again at any time.

I smoke and can confirm that smoking is indicated by the TVOC sensor.