Patent ID: 7341449

Claim:
A method which may be used for heat treating objects in an enclosure, said method comprising: a) heating at least one zone of said enclosure, wherein said enclosure comprises: 1) a treatment zone; and 2) passages, wherein said passages comprise: i) at least one entrance passage located between said treatment zone and the exterior of said enclosure; and ii) at least one exit passage located between said treatment zone and said exterior of said enclosure; b) injecting a gaseous first fluid into said treatment zone; c) transporting said objects through said treatment zone; and d) injecting a gaseous second fluid near said passages, said second gaseous fluid comprising a mixture of at least two gases, wherein: 1) at a first temperature present in said passages, the density of said second fluid is greater than the density of said first fluid, 2) air surrounds said enclosure and is at a second temperature less than said first temperature, and 3) the density of said second fluid at the first temperature is approximately equal to or greater than a density of air surrounding said enclosure at said second temperature.