Detailed chemical kinetics typically involve a large number of chemical species and a wide range of time scales. In calculations of chemically reactive flows, dimension-reduction techniques can be used to reduce the computational burden imposed by the direct use of detailed chemistry. In the reduced description, the reactive system is described in terms of a smaller number of reduced composition variables (e.g., some "major" species) instead of the full set of chemical species. Reactive flows exhibiting complex dynamics are especially challenging for dimension-reduction techniques and therefore provide more rigorous validation for such methods. Following the work of Brad et al. [Proc. Combust. Inst. 2007, 31, 455],1 in this paper, we demonstrate the capability of the Invariant Constrained-equilibrium Edge Pre-Image Curve (ICE-PIC) dimension-reduction method [J. Chem. Phys. 2006, 124, Art. No. 114111]2 through calculations of the oxidation of a CO/H2 mixture in a continuously stirred tank reactor (CSTR) at low pressure. The detailed chemical kinetics employed involves 11 species and 33 reactions. The system exhibits complex dynamics such as oscillatory ignition, oscillatory glow, and mixed mode oscillations. It is demonstrated that with five represented species the reduced description provided by the ICE-PIC method is able to quantitatively reproduce the observed complex dynamics. Moreover, the reduced description accurately predicts the boundaries of slow reaction, oscillatory ignition and the steady ignited state.