In addition to the spot I have a B&Q CO detector for the Bolkow 208, where all the ventilation comes past the exhaust, and the cockpit is draught-free.. Never had a bleep. Placed near air inlet
The Jodel cockpit is draughty, with air coming in from above my head.
It has a spot detector, which has successfully responded to exhaust leaks. I had the B&Q one in my flight bag, on the passenger seat. After almost an hour, doing steep turns and stalls, it went off. I returned and it kept screaming until I put it outside. The spot hadn't changed. Before the next flight, I examined the exhausts, and rubbed my finger at joints looking for soot. Nothing. I flew. Still alive.