Laser‐induced plasmas obtained during a welding process have been studied. Spectroscopic diagnostics and an integrating sphere collecting the reflected CO2light are the principal diagnostics used in order to determine the spatial variations of the microscopic parameters such as electron density and temperature, and the energy absorption during this process. For several experimental processing conditions of shielding gases, the main perturbing effects such as absorption and refraction of the CO2laser radiation are quantified. Several possibilities for reducing these perturbing effects are then discussed.