Review on UEi Test Instruments CO71A Handheld Digital Carbon Monoxide Detector, Portable CO Meter with 0-999ppm Range, Visual and Audible Alerts, CO Monitor Tester + Battery Included by Daniel Jackson

Good readings at low exposure when CO can be detected from ambient air. It is difficult to ensure that the air is actually properly exposed to the sensor inside, as it is in an awkward location. The sensor holes are small and you have to move the meter in jerky motions to get an accurate reading. This is helpful when exposed to ppm above 30. But anything below that can be difficult to read. He needs a pump.