The purpose of the present work is, firstly to study experimentally the factors which influence the performance of a ow-powered vortex stabilised torch constructed by Tioxide (UK) Ltd, which will operate with air instead of oxygen as the plasma gas. The second part of the work is concerned with the design of a new co-axial plasma torch. After a definition of a plasma and its generation, the different types of torches used in the process industry are presented. The electrical characteristics of the plasma arcs and their potential distribution, as weIl as metal vapour emission from the electrodes, are discussed. The stabilisation of the arc in an electric circuit was studied, and a general model of the power supply circuit incorporating either resistances or in ductances was formulated. The axial arc root position on the surface of the rear electrode has been investigated, and the main influencing factors identified and discussed. The effect, on the torch characteristic, of adding a small amount of argon to the plasma gas was studied and thermal efficiency of the torch and plasma jet enthalpy evaluated, as a function of argon percentage. Several cathode/ anode materials and combinat ion were investigated and the erosion rate determined for each arrangement, under typical operating conditions. The two line ratio spectroscopic technique (Ornstein method) was used to investigate the temperature profile of the free burning plasma jet, at different stations above the nozzle exit. Two quite different plasma torch designs with magnetically controlled arcs were designed and the results of these experimental tests are presented. Finally, the injection of toxic liquid is discussed and two reaction chamber designs presented together with suggestions for further work.