The root side of the weld should also be protected by a gas in order to prevent oxidation. Moreover, a backing gas also gives the root a more attractive appearance and reduces the risk of root defects.Before starting to weld, the root side of the weld should be pre-purged with shielding gas in order to reduce the oxygen concentration in particular. MISONÒ Shielding Gases provide optimum protection together with a shielding gas device designed for the application.