Product review (5 stars): Great Product
Measures the CO2 in the room quite well.  I suffer from insomnia.  It's nice to know how your A/C or fan or heat or an open window is effecting the room.  This thing does the trick.  I know I sleep really well under 500ppm, but can sleep usually under a 1000 ppm.  Nice to know the actual temp by your bed rather than by the A/C, or at the humidifier.