Commercial jets are not required to have Carbon Monoxide detectors? The Cessna 172 I flew for flight training had one of these $5 color-changing detectors. Sure

Commercial jets are not required to have Carbon Monoxide detectors? The Cessna 172 I flew for flight training had one of these $5 color-changing detectors. Surely we should have comprehensive monitoring for CO and volatiles. https://www.mypilotstore.com/MyPilotStore/sep/4420 https://www.mypilotstore.com/MyPilotStore/sep/4420