Thanks
i use this one
@Peter_Paul, this is exactly the model we wound up buying for €25 in Berlin. How has it been working for you? Do you get any non-zero indications?
I have been using a simple CO detector which is (in theory) indicating levels above 5ppm in both a PA28 and a C152 during training. It has a peak memory function so I don’t have to look during the flight to see whether it detected anything below the alert level.
It never indicated anything.
To test it, I left it outside under the wing on the exhaust side. I just started up, and shut down again after thirty seconds, and the thing was blaring (don’t remember what it read, though).
Maybe next time I will leave it on the wing next to the door, see what happens…
You can use the CO monitor to find peak EGT, when you reach the lowest CO value, you have the best mixture 
PS: No use to test your CO monitor with car exhaust gases. They do not contain any CO these days due to lean combustion and catalytic converters. Suicide by car exhaust is also a thing of the past…
That’s actually another advantage of flying LOP … very little CO
I test it every 4-5 month by holding it close to one of the cat free towing tugs we have at the airfield (non electrical ) it does read so i guess it is working
and in my previous c182 i got sometimes when with open window on ground some redings as well
I have the little CO 300 from aircraftspruce. Most of the time shows 0, sometimes 1 …
Be sure to have the unit calibrated / renewed every year or two year at maximum. Sensors do wear out. Some, especially the cheaper units, don’t say anything on lifetime, or calibration. It can give a false feeling of safety. In my experiance, sensors typically will make it upto 2 years being within tolerance.
