An unsteady state method and a steady state method of the permeable system have been developed to measure the respiration rate of fresh produce and to estimate the parameters of enzyme kinetics based respiration model. In the unsteady state method, changes in O-2 and CO2 concentrations over time inside a permeable package are curve-fitted to appropriate nonlinear equations, respiration rates are calculated by combining the derivatives of the nonlinear equations and the gas permeations through film, and then the parameters of the enzyme kinetics based respiration model are obtained from multiple linear regression of respiration data versus gas composition. In the steady state method, respiration rates are calculated from steady state gas permeations of several packages, and curve-fitting of the data produces the respiration model parameters. The applicability of the two methods was verified successfully using several independent sets of experimental data. The advantage and disadvantage of the methods are discussed.