The invention relates to the monitoring of the state of produce within transport containers, with particular application to dynamic monitoring of the respiration rate of produce in controlled atmosphere container systems used in cargo container transportation. A method is provided for tracking, over an extended period, the respiration rate of produce contained in a leaky transport container, including the steps of, at intervals during said extended period, for a prescribed period, being a respiration rate data block (RRDB) cycle, ensuring that there is substantially no air passage between the interior and the exterior of the transport container other than leakage, identifying the leakage rate of the transport container, measuring, at intervals over said RRDB cycle, the concentration of one or more constituent gases in the transport container as the produce respires; and calculating, at a logic unit, from said measurements of concentrations of said one or more constituent gases and said leakage rate, a respiration rate of the produce for each RRDB cycle. In a controlled atmosphere container system, the method involves, under control of a controller, at intervals during said extended period, suspending controlled atmosphere (CA) operation and initiating a respiration rate monitoring (RRM) mode, in order to measure the concentration of the one or more constituent gases in the transport container as the produce respires, from which the respiration rate can be calculated.