Correlations that allow determination of gas film mass transfer coefficients (k(G)a(t), k(G)a(w)) and liquid film mass transfer coefficients (k(L)a(w)) for packing materials used in biofilters and biotrickling filters for air pollution control are presented. Lava rock, polyurethane foam cubes (PUF), Pall rings, porous ceramic beads, porous ceramic Raschig rings, and various compost-woodchips mixtures were used as packing materials. The functionality of gas and liquid velocity on mass transfer coefficients (k(G)a(t), k(G)a(u)), k(L)a(w)) obtained experimentally (see Part I of this paper) was correlated using modified Onda-type equations. The correlation equations helped to better understand the sensitivity of gas and liquid velocities on mass transfer, and the effects of packing wetting. Each packing had a different functionality with gas and liquid velocity and different wetting property, hence different correlation equations were needed for the different packing materials. Most of the fitted data fell within 20% of the experimental values. (c) 2007 Elsevier Ltd. All rights reserved.