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 Jesus Carlson

We use this device on two of our planes because carbon monoxide is a major hazard on planes. This is the best. Over the years I have tried various devices from other manufacturers. Some are cheap cardboard with a dot to change color with CO. Others are expensive and some are very expensive and turn off after 2 years even if you turn off the device after every flight. Forensic CO monitors are small but give very clear warnings and tones. The price is great as it's 1/3 the price of the 'best' monitor I've bought before. The only thing missing from this device are "End of Life" warnings. Don't worry we will buy two more when this happens. We have one on every aircraft, positioned so that it is in the pilot's field of view. Highly recommended.