Abstract: A method of determining the concentration of an exhaust component in a gas turbine engine includes measuring the concentration of the selected component at a single location, and using the measured concentration in a simple equation which yields a calculation of concentration in the engine exhaust. Use of this method requires that a measurement be taken for only one of multiple combustors in an engine, but the result is valid for the entire engine. Thus, the method can reduce the cost of design and development of new combustors for gas turbine engines, since it does not require that multiple combustors be built before the engine is tested. The sampling of the component of interest is done at a point sufficiently downstream that the concentration of the component has become relatively stable. The invention also includes an engine having one or more combustors modified to include a probe, and its associate analyzer, at an optimum location.