Design of active modified atmosphere packaging for vegetables was studied by developing a mathematical model predicting gas changes and based on the following independently evaluated parameters: vegetable respiration rate, film permeability, and oxygen absorption kinetic of the absorber. A step-by-step model validation was performed on a tomatoes/low-density polyethylene pouch/commercial iron-based scavenger system at 20 °C. Without optimization, the model fit experimental data with root mean square error (RMSE) value lower than 1.5. Oxygen absorbers had a strong influence on transient period characteristics by reducing their duration (50 and 100 h with and without absorber, respectively) and suppression of the CO2 peak owing to a rapid oxygen depletion.