Abstract: An atmosphere control system for the cab of a self-propelled combine has its principal components arranged for series flow and mounted compactly on a rear portion of the floor of the cab. A pressurizing blower injects fresh air into an upstream filter chamber through a translational inertial precleaner which discharges any removed dust along with bleed air vertically downwards through the floor of the cab. A filter further cleans fresh air as it continues into the system, to pass through a heat exchanger and into circulation by a circulation blower and suitable ducting. Both precleaner and fresh air filter are accessible through a door in an outside wall of the cab.