A simulation tool for the numerical solution of large kinetic systems with special emphasis on examples from atmospheric chemistry and combustion is presented. The chemical mechanism has to be provided in readable ASCII format, whereas the program is able to read the TROPOS syntax for chemical systems and also the widely used ChemKin format. From this, a system of ordinary differential equations is generated internally and solved numerically by Rosenbrock-type methods. Efficiency is obtained by carefully exploiting the sparsity structures of the Jacobian. Additionally, another approach is implemented, where the direct evaluation of the Jacobian is no longer required. The effects of both strategies are investigated by simulating detailed atmospheric multiphase mechanisms and gas-phase combustion mechanisms.