Penning ionization (PI) processes for cold Rydberg alkali metal atoms are investigated. Contrary to the reference case of a hydrogen atom, the corresponding autoionization widths demonstrate a sharp dependence (by orders of magnitude) on the orbital quantum numbers of the atoms exposed to long-range dipole-dipole interaction. An important feature of PI is the nontrivial dependence of its efficiency on the size of Rydberg particles. For all types of alkali atoms, the existence of optimal Rydberg pairs has been demonstrated (highly asymmetric configurations of Rydberg pairs), which lead to an explosive intensification (by several orders of magnitude) of the formation of free electrons due to PI processes. This property makes PI an important source of the formation of primary charged particles during the formation of cold Rydberg plasma. The presented numerical data for potassium atomic pairs demonstrate a significant effect of the Förster resonance on the values of PI rate constants.