This paper presents results on a new pulsed–periodical streamer operation regime of a packed-bed reactor in argon at sub-atmospheric pressures fed by a steady-state high voltage. The use of a direct current (dc) supplying voltage instead of an alternating current one allows a large reduction in the requirements of the dielectric properties of the pellets—in the case of the dc regime it is possible to use non-expensive glass beads instead of ceramic pellets. A self-running streamer regime was attained due to a change in the background gas producing non-thermal plasma in the packed-bed reactor, i.e. the electronegative gas (air) was changed for an electropositive gas (argon). The new discharge regime increases the volume of the treated gas, and consequently, the total productivity of the packed-bed reactor. An analytical model is proposed to calculate the most important streamer parameters like the initial plasma density and cross section of a single streamer, and the total number of streamers in each current pulse.