Abstract: The present invention relates to a method for controlling weld quality. The method comprises the steps of producing a shield gas curtain around the heat source and producing a shroud gas curtain spaced radially outward from the shield gas curtain, wherein the shroud gas curtain comprises a radially outward component of velocity. The shield gas curtain and the shroud gas curtain are configured to control the resultant mechanical and/or surface properties of the weld. The present invention also relates to a method for substantially confining and concentrating shield gas about the vicinity of a welding site, and a method for substantially recovering and reusing a shield gas in a welding operation.