Air entrainment by a flow of loose material is the primary cause of dust releases during handling of such materials. Computing the flow rate of air ejected by the material is a prerequisite for ventilation system design. An additional consideration is that mining industries normally handle polydisperse materials. The goal of our study is to design a method for computing the flow rate of air entrained by dry loose material while accounting for its particle-size distribution. We rely on a phenomenological method as we describe an interpenetrating continuum, "falling particles - air". We propose a probabilistic approach for determining the aerodynamic drag coefficient for freely falling particles of polydisperse material. A differential equation is obtasined for air entrained by this material. The effect of particle-size distribution of the material being handled is considered together with methods for determining the average particle diameter on the flow rate of ejected air. (C) 2020 Elsevier B.V. All rights reserved.