The remaining parameters in the model characterize the environmental conditions in the plane. We parameterized the model to reflect the environmental conditions in a Boeing 747 airliner; parameter values were obtained from Boeing [14] . where N i represents the number of passengers in cabin i and ρ represents the volumetric breathing rate of the source case (ρ = 0.3 m 3 /h) [15] . We obtained estimates for C i (t), i = 1...4 by integrating our sequential box model.