In this work, we extend the base case model for debutanizer fouling in our previous work toward oxygen chemistry ("oxygen-perturbed model"), as illustrated in Fig. . We follow a similar modeling method as presented in our previous work. A general flow sheet of this work can be found in Fig. . First, we model the separation chain downstream of the steam cracker using Aspen Plus, where we introduce dissolved oxygen to the debutanizer feedstock at an air-saturated concentration for the extreme-case scenario study. We generate the polymerization and autoxidation mechanism in the bulk liquid at each tray, condenser, and reboiler, using Reaction Mechanism Generator (RMG), a software package for automatic mechanism generation, originally developed by the MIT Green Group, and now developed as an open-source project. To obtain a mechanism with a reasonable size, we use a hard cutoff for oligomer size during mechanism generation. We want to recover the chemistry related to the truncated larger oligomers. The Anderson-Schulz-Flory (ASF) distribution is an expression that predicts the weight distribution of oligomers with respect to its number of monomer units, developed from ideal chain-growth polymerization. Using the ASF distribution, we can estimate the concentration of truncated larger oligomers based on those of the smaller oligomers in the mechanism. We modify the ASF distribution expression to accommodate the combination of ordinary free radical polymerization and autoxidation to better estimate the oligomer distribution under molecular oxygen contamination. The film growth mechanism at the surface of each tray, condenser, and reboiler is modeled using a variant of fragment-based modeling, 20 a type of lumping well-suited for modeling unselective chemistry of mixtures containing macromolecules. We update the fragment-based reaction template presented previously to include important autoxidation reactions. We simulate the oxygen-perturbed fouling model with a simulation scheme similar to our previous work using ReactionMechanismSimulator.jl (RMS), a Julia software package for simulating large chemical kinetics models developed recently by the MIT Green Group. As shown below, the new oxygen-perturbed model predicts a faster fouling rate in some trays of the column and prompts us to consider diffusion limits when simulating the fouling growth.