A limited area, off-line, Eulerian atmospheric transport model has been developed. The model is based on a terrain following vertical coordinate and a mass conserving, positive definite advection scheme, with small phase and amplitude errors. The objective has been to develop a flexible, all purpose off- line model. The model includes modules for emission input, vertical turbulent diffusion and deposition processes. The model can handle an arbitrary number of chemical components and provides a framework for inclusion of modules describing physical and chemical transformation processes between different components. Idealized test cases as well as simulation of the atmospheric distribution of 222Rn demonstrates the ability of the model to meet the requirements of mass conservation and positiveness and to produce realistic simulations of a simple atmospheric tracer.