Abstract: A method and apparatus for heat treating objects in an enclosure, where the enclosure has an inlet passage, an outlet passage, and a treatment zone. Gaseous first fluid is injected into the treatment zone and the objects to be treated are passed through the treatment zone. A second fluid, with a density greater than that of the first fluid, is injected near the inlet and outlet passages.

Abstract: The process is carried out in an enclosure (21) located in a surrounding gaseous fluid and defining an internal treatment zone (31). The enclosure (21) comprises an entrance passage (32) and an exit passage (33). This process comprises the following steps: (a) the treatment zone (31) is heated; (b) a gaseous treatment fluid is injected into the treatment zone (31); (c) the said objects (12) are transported through the said treatment zone (31); (d) a gaseous isolating fluid is injected in the vicinity of at least one of the said passages (32, 33). In step (d), the density of the said gaseous isolating fluid at the temperature found in the one or more of the said passages (32, 33) is greater than the density of the gaseous treatment fluid inside the oven. Applicable to the assembling of electronic boards by soldering.