R. J. Lipton has introduced a reduction method which permits a process assumed to be interruptible to be reduced to an uninterruptible process without affecting the behavior of the rest of the system to which the process belongs. Demonstration of the adequacy of a system of reduced processes is considerably less complex than such a demonstration for systems involving unreduced processes. Reformulation of Liptons ideas in Special petri net theory leads to the formalization of some informal aspects of Liptons method and permits a weakening of his reducibility conditions on processes without loosing any of his results.