Roaster off-gas systems play an important role in reducing SO2 emissions to the atmosphere and in ensuring the satisfactory operation of nickel smelters in accordance with environmental regulations. In this paper, the dynamic models for an industrial roaster off-gas system are developed using mass continuity, momentum, and energy conservation laws. Industrial measured pressure data are compared with the steady-state pressure models that are the special case of the developed dynamic models, and good agreement is obtained. On the basis of the developed dynamic models, the effects of important variables on the dynamics of the off-gas system are studied via simulations. The developed dynamic models provide a necessary basis for high performance control development for roaster off-gas systems.