A three-dimensional mathematical model was developed to predict gas distribution as a function of time inside
a perforation-generated modified atmosphere bulk package using the principle of diffusion in a ternary gas mixture.
Product and air space layers in the package were considered. The model incorporates simultaneous oxygen consumption,
carbon dioxide generation and porosity in the product layer. An implicit-explicit finite difference numerical technique was
used to solve the transient three-dimensional equations. The mathematical model closely predicted measured gas
concentrations in different types of packages. The results show package CO2 concentration increased; whereas, O2
concentration decreased with increasing distance from the perforation. Higher gas concentration gradients were obtained
in packages with thin air space thickness. Thus the effective distance from the perforation is an important parameter for
gas concentrations in perforation-generated modified atmosphere bulk package.