This paper reports dielectric recovery property measurements of CO2 and Air arcs under free recovery condition. In these measurements, the arc current and the voltage applied to the free recovery arcs were controlled with a high accuracy in time using power semiconductors. The recovery properties were measured by changing the application delay time t(d) of the recovery voltage with a peak of 8.2 kV. As a result, 200 L/min of CO2 gas flow needs t(d) = 165 mu s to withstand the quasi-TRV application with 50% probability of arc re-ignition; while 200 L/min of Air gas flow requires t(d) = 220 mu s for the same purpose.