This paper presents a comprehensive treatment of the parametric sensitivity and runaway in fixed bed reactors with one dimensional pseudo homogeneous dispersion model (ODDM). In this case, we find the existence of multiplicity and determine the runaway criterion through the critical isodisper sion curve. The calculated results indicate when the axial dispersion is relatively small, the impact of the axial dispersion on the parametric sensitivity may be neglected; but when the axial dispersion is large, this impact must be considered.
