The BLP dispersion model was developed specifically for aluminum reduction plants. It is part of the UNAMAP version 4 collection. Aluminum reduction plants are a complex arrangement of emission sources, composed of parallel, low-level, buoyant line sources called potrooms interspersed, typically, by short point sources. In addition to theoretical considerations, BLP is based on extensive wind tunnel simulations of two reduction plants and an SF6 field study tracer program at one of the plants. The model has been verified using two years of SO2 measurements at the second reduction plant. The major features of the BLP dispersion model are: UTM or line source oriented coordinate system; multiple point source and finite buoyant line source capability; finite buoyant line source plume rise, plume enhancement due to multiple line sources; vertical wind shear in plume rise formulations for both point and line sources; transitional plume rise; incorporation of building downwash in both dispersion and plume rise calculations for point and line sources; terrain adjustment plume path coefficients; time-dependent pollutant decay; source contribution concentrations; and flexible post-processing package.