Monte Carlo simulation techniques based on the independent reaction times (IRT) approximation are used to model the nonhomogeneous chemistry that takes place between 10 -12 and ∼10 -6 s in the tracks that are generated by ionising radiations in liquid water. Our simulation code TRACIRT, whose execution follows that of the codes TRACPRO and TRACELE described in the preceding paper, allows one to account adequately for the stochastic nature of the occurence of the reactions. In addition to its accuracy and rapidity, the IRT approach also allows one to incorporate the most fundamental elements that control the reaction kinetics, that is, the Bownian diffusion of the reactive species, their mutual Coulombic interactions, the effects of radical spin correlations, and the activated processes that make the reactions only partially diffusion-controlled. The code TRACIRT is able to simulate the nonhomogeneous chemistry that pertains to proton and electron tracks of various linear energy transfers (LET) ranging from ∼0.3 to 20 keV μm -1 . The time dependence that we obtain for the radiolytic yields compares well with the observed values. The simulations also provide valuable information on the time range over which the different reactions take place and on their tracks allows one to vary systematically the LET (through appropriate choices of the incident proton energy) and to characterise quatitatively its influence on the time-dependent yields.