An assembly in an imaging apparatus including a developer unit and a toner cartridge having a pressure equalization system for equalizing a pressure differential between a toner reservoir in the toner cartridge and a toner sump of a developer unit containing ingested air. A ducted shutter that opens and closes an exit port on the housing of the toner cartridge in combination with a passageway in fluid communication with a duct in the shutter and the toner reservoir forms an airway, and when the toner cartridge is mated with a developer unit of the imaging apparatus and the shutter is in the open position, exiting toner leaves the cartridge through the exit port and enters the developer unit while air entrained within the developer unit enters the toner reservoir via the exit port and airway equalizing pressure between the toner cartridge and the developer unit.