Abstract: An air distribution system for a vehicle cab. The system uses two blowers: a first constant-volume blower for drawing fresh outside air into the cab and a second variable-speed blower for recirculating the inside air. An air filter is positioned upstream of both blowers for filtering out dust and other contaminants. As the fresh outside air passes through the first blower, it is mixed in a mixing zone with inside air which passes thorugh the second blower. This intermixed air is then passed through a temperature controller which includes a heating unit and an air conditioning unit. The temperature controller treats the air stream before it is routed through a series of ductwork to various parts of the operator's compartment of the cab. This two-blower air distribution system is a vast improvement over conventional air distribution systems in that it always provides for a positive air pressurization within the cab thereby preventing the influx of dust.