Abstract: An apparatus having a first and second zones, for destroying hazardous compounds of a first and second types respectively present in a gas stream. The first zone has a first live electrode and a ground electrode. The first live electrode and the ground electrode define a first gas passage. These electrodes are excitable at a first energy level for generating a first electric field capable of generating a plasma in a gas flowing through the first gas passage. The second zone has a second live electrode spaced apart from the ground electrode. The second live electrode defines with the ground electrode a second gas passage communication with a downstream end of the first gas passage. The second live electrode is excitable at a second energy level for generating with the ground electrode a second electric field capable of sustaining the plasma in the gas flowing through the second gas passage.