This is an excerpt from a report made to the Aviation Safety Reporting System. The narrative is written by the pilot, rather than FAA or NTSB officials. To maintain anonymity, many details, such as aircraft model or airport, are often scrubbed from the reports.
After doing a prolonged run up in the PA-28 on Runway XX (after having massive avionics upgrades at a shop on the field) we noticed slight elevations in CO (Carbon Monoxide) in the cockpit. 25-40 ppm.
My student and I were aware and I said to keep the window open and keep the heat and vents closed (which resolved the issues) and the levels went back down to an acceptable range.
After being cleared to depart with a right turn out to the east of the airport, the student and I briefed our takeoff and emergency action that would be taken in case of an emergency.
A few seconds after rotating I stated feeling symptoms of what I believed to be from the CO. I was going to give the plane to my student so I could open the door for air as he warned me of the sensor reading close to 250 ppm of CO.
I got tunnel vision as well and extreme dizziness and a headache and told him to open the window, which is in the left side.
Fearing we only had seconds before I lost consciousness and that he would be not far behind me, I entered into a steep right bank nose lose attitude (received priority) and tried to make it to the intersecting runway. I was unable to make it to the runway and was able to land on the taxiway.
As soon as we stopped I opened the door and then responded to the tower and waited for emergency personnel.
A mechanic on the field informed us the next day there was a crack in the exhaust (unsure of the size) in a place I would not have been able to see.
I believe my actions were correct both in timing and place of landing.
Primary Problem: Aircraft