Flight Crew Commercial; Flight Crew Flight Instructor; Flight Crew Instrument; Flight Crew Multiengine
Flight Crew Last 90 Days 136; Flight Crew Total 389
Situational Awareness; Physiological - Other
Aircraft Equipment Problem Less Severe; Flight Deck / Cabin / Aircraft Event Illness / Injury; Flight Deck / Cabin / Aircraft Event Smoke / Fire / Fumes / Odor
Flight Crew Landed in Emergency Condition; Flight Crew Returned To Departure Airport
Aircraft; Human Factors
Exhaust gas leak on board while conducting a biannual flight review. Upon entering left midfield downwind; I noticed a smell of exhaust fumes in the cockpit and requested right turn out direct to ZZZ. Tower approved this turn out and we headed direct to ZZZ at 2500 feet. Upon reaching 2500 both pilot and I (instructor) began feeling symptoms of carbon monoxide poisoning. We slowed the aircraft down momentarily to open the windows to get additional fresh air into the cockpit. We then proceeded to close the windows so we could get our speed up to land back at ZZZ for a straight in approach. We requested all other traffic in the area to heed us so we could arrive with no delay and everyone flying at ZZZ made sure to stay clear and help us arrive as quickly as possible. I did not officially declare an emergency with ATC as it was more vital to communicate my intentions with the traffic currently flying at ZZZ which proved to be a huge help to us; however I should have declared an emergency with the other tower and landed there as soon as I smelled the exhaust rather than try to make it back to ZZZ.
C172 instructor pilot reported detecting exhaust fumes while in the traffic pattern and elected to depart the pattern and return to home base.