Abstract: A system adapted for removable placement in a security enclosure fitted into the wall of a refrigerated container for respiring perishables, and for monitoring and controlling, continuously and dynamically, over a programmed, desired time, the concentration of oxygen, and the concentration of dioxide, in such a container atmosphere where the concentrations of these gases vary over time as the perishables respire, includes devices for sensing, separately, the concentrations of oxygen and carbon dioxide in the container atmosphere, devices for establishing setpoints or desired values of oxygen and carbon dioxide atmospheric concentration within the container, and for changing those setpoints, over time, depending on the nature of the perishable and other variables, and for maintaining the atmospheric concentrations of oxygen and carbon dioxide at desired setpoints for desired programmed times by admitting outside air into the container, as a source of oxygen, and by scrubbing to remove carbon dioxide, as necess