Abstract: A method of treating bituminous paving mixtures to reduce the amount of aggregate fines discharged into the atmosphere. Aggregate is fed into a charging end of an inclined drum mixer and is heated by a low-velocity gas stream to form steam from the moisture contained by the aggregate within a steam zone. Liquified asphalt is supplied to the aggregate in an asphalt injection zone as it moves downstream in the drum from the steam zone and coats the aggregate as it is tumbled and moved along the drum in a coating zone toward a discharge end. In the gas stream, the ratio of airflow into the drum mixer is accurately controlled with respect to the rate of fuel flow to a burner located at the charging end of the mixer, to consume during burner combustion all oxygen supplied by the airflow to produce a heated gas stream, thereby eliminating free oxygen from the interior of the drum mixer.