Gas curtain assemby for muffled continuous furnaces

A method of treating a metal object in a gas curtain assembly adapted to be inserted into a continuous furnace from the discharge end of the continuous furnace, which gas curtain assembly comprises at least one structure of substantially vertical tubes on both sides of and supporting a top horizontal gas curtain tube, forming an interconnected frame comprising at least one row of apertures for gas or fluid to pass through and forming a curtain of gas or fluid under the top horizontal gas curtain tube of the assembly, wherein the vertical tubes are engaged with base horizontal tubes which extend longitudinally inside the continuous furnace, and wherein the base horizontal tubes are substantially transverse to the plane of the gas curtain assembly the method comprising supplying the gas or fluid to the at least one row of apertures through at least one of the base horizontal tubes, at least one of the vertical tubes, and the top horizontal gas curtain tube, and passing the metal object through the curtain of gas or fluid under the top horizontal gas curtain tube.