One should keep in mind that a main limitation in all radiative transfer computations comes from the accuracy of available collision rates and the temperature range where they are tabulated. At temperatures outside the interval given in the molecular data file, the collision coefficients will be linearly extrapolated. Moreover, one should also consider that the maximum number of levels is restricted in the code, so that high temperatures combined with high densities might produce non-vanishing excitation at levels that are neglected in the computation. Users should verify that the maximum level number is sufficient for their problem.
The program is not designed for strongly varying turbulence. The gradient in both the absolute value of the turbulent velocity dispersion and in the turbulence correlation length should not exceed the steepest gradient of either the systematic velocity or the density.
Due to the limited number of frequency points, systematic velocities may be at most one order of magnitude above the random velocities.