In a system and process for developing an imaged plate by contacting the plate with an alkaline developer, contained in a developer tank having a cover spaced over the developer level, the space between the developer level and cover is maintained at a concentration of carbon dioxide below ambient for a substantial portion of each day. Preferably, active carbon dioxide control is implemented in the space at least during idle periods, to maintain the concentration of carbon dioxide below about 100 ppm, preferably in the range of 0-10 ppm. The system has a first conduit with an extraction port in the space and a second conduit with a return port in the space. A canister of carbon dioxide scavenger material is fluidly connected between the conduits. A motorized air handling device fluidly connected with the conduits and scavenger material, draws air out of the space, passes the drawn air through the canister, and delivers the scavenged air back into the space. A special cover having the ports, can be fit over the developer to enhance the sealing of the space from ambient air and thereby improve efficiency.