Described herein are various embodiments of a reductant decomposition system. According to one representative embodiment, the reductant decomposition system includes an exhaust gas chamber including an inlet and outlet. The system also includes a first exhaust gas distribution component positioned within the chamber and communicable in exhaust gas receiving communication with the outlet. The first exhaust gas distribution component causes swirling exhaust gas flow patterns within the exhaust gas chamber. Additionally, the system includes a second exhaust gas distribution component positioned within the chamber and communicable in exhaust gas providing communication with the inlet. The second exhaust gas distribution component includes features that cause a swirling exhaust gas flow pattern within a space defined by the second exhaust gas distribution component. Further, the system includes a reductant injector coupled to the exhaust gas chamber. The reductant injector is communicable in reductant injecting communication with exhaust gas within the chamber.