A new method for the analysis of oxygen ingress into packages and optimized design solutions for multilayer barrier films incorporating an immobile noncatalytic oxygen scavenger within one of the layers are presented in this three-part series. The results are based on the theoretical framework of transient permeation through a dense reactive medium with a finite solute scavenging capacity. The target application was flexible and rigid plastic packaging for oxygen-sensitive products, and the goal was the minimization of oxygen ingress into the package within a predetermined timeframe. A predictive model for oxygen ingress was developed, and practical recommendations for the selection of layer material properties, layer sequencing, and placement of the scavenger within a layer to achieve this goal are provided. Part I introduces the concepts of reference and steady-state lag times for passive barriers to gas permeation. These concepts are expanded to include the scavenger exhaustion lag time for noncatalytic reactive barriers with an instantaneous scavenging reaction. The steady-state lag time concept is applied to the characterization of noncatalytic reactive barrier solutions with finite rates of the scavenging reaction using transient effective flux dynamics and the model Of Solute ingress into the package. T e model is based on the semipermeable reaction wavefront concept, which we developed. The corresponding passive-to-reactive film transition and its effect on the lag times are discussed. (c) 2006 Wiley Periodicals, Inc.