A method and apparatus that reduce release of dust generated during rotary dumping of rail cars in a dumping facility. The method includes removing dust laden air from a space bounded by a backside airflow diverter, a rotational frame, a first baffle and a second baffle while the rotational frame is rotating with a rail car by drawing the dust laden air through a secondary air intake that passes through the backside airflow diverter into a backside hood. A dust control apparatus includes a diverter, overlying a backside hood having a concave curved upper surface; and at least one secondary air intake positioned to pass through the diverter being located approximately where pressure in the backside hood remains neutral or negative relative to a pressure even there is a transient increase in air pressure in a lower portion of the backside hood.