Narrative:

My student and I had just completed practicing engine failure procedures during a simulated engine failure northeast of our home airport. While climbing out at the end of the practice procedure; at around 500 AGL; I was talking to the student about ELT operations when I noticed the indicator on our portable carbon monoxide detector was indicating the presence of carbon monoxide inside the cabin. I told my student 'we might have carbon monoxide in here;' and my student immediately replied he was feeling lightheaded. I immediately turned off our cabin heat and window defroster; which had been turned on to a low setting at the beginning of the flight; and instructed the student to open his window. I resumed control of the aircraft. At around 2;000 feet MSL I began to experience lightheadedness as well; which subsided after about a minute thanks to the fresh air coming through the window. We were 10 miles northeast of ZZZ at this time; inbound towards the airport; so I increased power to maintain best forward airspeed; listened to the ZZZ ATIS; and then called ZZZ ATCT. I advised the controller that we had a possible carbon monoxide issue inside the aircraft. The controller provided us with our pattern entry instructions and asked if we would like equipment standing by; to which I responded negative. By this time the student and I felt normal again; so I offered him the controls again; and he resumed control. When on the midfield right downwind to runway 5 at ZZZ; I again began experiencing some intermittent lightheadedness; as did he. I resumed control of the airplane and kept us fairly close to the runway so that we didn't spend more time than we needed to in the air. Upon landing; I immediately opened the cabin door to allow more fresh air inside the cabin; and both the student and I experienced relief once again. In retrospect it would have been a good idea to have a medic meet us at the ramp. I had not expected our symptoms to return after my student and I initially started feeling better. I am grateful to my company for installing the portable carbon monoxide detectors; as they aid in detecting potential carbon monoxide prior to the onset of severe physiological symptoms. My symptoms and those of my student were not severe enough to prevent us from maintaining control of the aircraft.

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Original NASA ASRS Text

Title: A flight instructor reports about the benefits of having a portable carbon monoxide detector that alerted them to the presence of carbon monoxide in the cabin of their Piper PA-28 Warrior aircraft. A feeling of intermittent lightheadedness was experienced twice prior to landing.

Narrative: My student and I had just completed practicing engine failure procedures during a simulated engine failure northeast of our home airport. While climbing out at the end of the practice procedure; at around 500 AGL; I was talking to the student about ELT operations when I noticed the indicator on our portable carbon monoxide detector was indicating the presence of carbon monoxide inside the cabin. I told my student 'We might have carbon monoxide in here;' and my student immediately replied he was feeling lightheaded. I immediately turned off our cabin heat and window defroster; which had been turned on to a low setting at the beginning of the flight; and instructed the student to open his window. I resumed control of the aircraft. At around 2;000 feet MSL I began to experience lightheadedness as well; which subsided after about a minute thanks to the fresh air coming through the window. We were 10 miles northeast of ZZZ at this time; inbound towards the airport; so I increased power to maintain best forward airspeed; listened to the ZZZ ATIS; and then called ZZZ ATCT. I advised the controller that we had a possible carbon monoxide issue inside the aircraft. The controller provided us with our pattern entry instructions and asked if we would like equipment standing by; to which I responded negative. By this time the student and I felt normal again; so I offered him the controls again; and he resumed control. When on the midfield right downwind to RWY 5 at ZZZ; I again began experiencing some intermittent lightheadedness; as did he. I resumed control of the airplane and kept us fairly close to the runway so that we didn't spend more time than we needed to in the air. Upon landing; I immediately opened the cabin door to allow more fresh air inside the cabin; and both the student and I experienced relief once again. In retrospect it would have been a good idea to have a medic meet us at the ramp. I had not expected our symptoms to return after my student and I initially started feeling better. I am grateful to my company for installing the portable carbon monoxide detectors; as they aid in detecting potential carbon monoxide prior to the onset of severe physiological symptoms. My symptoms and those of my student were not severe enough to prevent us from maintaining control of the aircraft.

Data retrieved from NASA's ASRS site and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.