A method of using a burner-based exhaust replication system to generate exhaust that contains nitrogen dioxide (NO2). An example of such as system is a system used to test automotive exhaust aftertreatment devices. A fluid that decomposes to generate NO2 as one of its decomposition products is selected. The fluid is heated thereby generating NO2, with the amount and duration of heating is controlled to result in a desired decomposition extent of NO2 from the fluid. The fluid is then delivered to an exhaust stream of the system.