The Lombardo-Fink-Imbihl (LFI) model for the NO + NH3 reaction on Pt {1 0 0} consists of seven coupled ordinary differential equations (ODES). Here, we present a numerical analysis for relaxation oscillations in the LFI and show that it cannot, be adiabatically reduced to two coupled ODES. We argue that this is because of the explicit consideration of the trapping processes of NO from 1 x 1 to hex phases in the kinetic mechanism of the reaction. Our analysis shows that an adiabatic reduction to three coupled ODES can be achieved. Moreover, we examine the hysteretic behavior in detail. (C) 2003 Elsevier B.V. All rights reserved.