Exposure to carbon monoxide (CO) can cause harmful health effects depending on its concentration and duration of exposure. Exhaust system failures in general aviation (GA) aircraft can result in CO exposure which, in turn, can lead to an accident. This research was performed in order to obtain insight into the causes of CO-related accidents/incidents in GA aircrafts through the analysis of historical data from the NTSB accident/incident database. The results indicated that CO related accidents/incidents occur throughout the year and that the muffler was the most common source of CO leakage. This was found to be the case even though accidents due to muffler and exhaust system leakage were more prevalent in the colder months. This paper reviews the data and presents the results of the analysis.