This paper calculates the critical reduced breakdown field of hot SF6 gaseous mixture based on the solution of a two-term Boltzmann equation for the electron energy distribution function (EEDF) using improved cross section data, bearing similarities to the residual plasma in the dielectric recovery phase of a high voltage circuit breaker. The influence of species composition on the dielectric properties, in cases of departure from chemically equilibrium which takes place during the arc extinction, was analyzed considering the species evolution by a kinetic model during the decaying process of gas blast SF6 arc. It is found that when departure from chemical equilibrium takes place, the critical breakdown field is reduced in the high temperature range.