Review on Fast Low-Level Carbon Monoxide (CO) Detector for Cars, Vehicles, and Aircraft - 9ppm Alarm, Ideal for Police, Pilots, Travel, Buses, and Trucks, Compact Metal Body (2oz) by Bob Maldonado

If you look at this product you will know that there are far cheaper and less complicated versions to choose from. I needed this for my Sprinter van which has a diesel heater and I wanted something inside the van to signal rising CO2 levels. I tested the cheaper versions by placing them near my heater outlet (on the outside of the van) with mixed results. This little device worked almost immediately after the same test. In fact, a few days ago I was making coffee in my van with a Jetboil and it started beeping (doors and windows opened) - while the cheaper versions of First Alert and Kidde made no sound. Would definitely recommend this - my only complaint is the weak adhesive on the back (had to use a screw).