Carbon monoxide indication during flight involving Piper PA-28, VH-PZG near Bankstown Airport, New South Wales, on 8 March 2021

At the top of climb, at about 4,000 ft near Warragamba Dam, the instructor detected a faint exhaust gas smell and recalled feeling a little more tired than when they took off and mildly lightheaded. The instructor then looked up at the carbon monoxide detector and observed a localised discolouration (indicating the likely presence of carbon monoxide in the cabin).