Method of analyzing vehicle emissions and in-flight gas analysis apparatus

A method and apparatus for measuring the concentration of one or more emission gases in the exhaust of a vehicle, including a conventional gas analyzer and a transducer for monitoring at least one parameter directly related to the operating condition of the vehicle. Samples of gas emissions are supplied to the gas analyzer and the transducer is monitored while the vehicle is operated in a convention manner. A running history of readings of exhaust gas concentration(s) of interest is maintained during vehicle operation with earlier readings being supplanted by recent ones. Upon the occurrence of a predetermined event, the running history is preserved in order to provide a correlation between the exhaust gas concentrations and known operating parameters of the vehicle.