Plasma or TIG welding or cutting method using non-oxidizing gas containing a low content of impurities, in particular H2O and/or O2

The non-oxidising gas contains a proportion of oxygen based impurities of less than 80 ppmv and a proportion of water vapor based impurities of less than 400 ppmv and in that the ratio of the oxygen based proportion to the water vapor based proportion in the gas is such that:- 0 at most (O2) / (H2O) at most 1/3. A method of working with an electric arc, in which a torch is fed with at least one non-oxidising gas. The torch is equipped with at least one electrode of pure or alloyed metal and the non-oxidising gas contains a proportion of oxygen based impurities of less than 80 ppmv and a proportion of water vapor based impurities of less than 400 ppmv. The ratio of the oxygen based proportion to the water vapor based proportion in the gas is such that:- 0 ≤ (O2) / (H2O) ≤ 1/3. The utilisation of this method for a cutting operation applied to steel, aluminum or stainless steel structures and the non-oxidising gas used in the method are also claimed.