Abstract: Cermic materials (i.e. architectural face-bricks) are fired in a tunnel kiln of the type having a firing zone and a downstream cooling zone. The cooling zone is segregated into indirect and direct cooling zones via a sealed gate structure therebetween. The heated gases in the indirect cooling zone are thus preliminarily cooled by suitable means (for example, a heat exchanger) and the cooled gases are returned via a closed-loop path to the indirect cooling zone. The fired ceramic materials in the direct cooling zone are finally cooled by the direct introduction of an oxygen-rich gas (i.e. ambient air). In such a manner, a reducing atmosphere may be maintained in the firing zone and in the indirect cooling zone while final cooling of the bricks occurs in the direct cooling zone. Thus, the oxygen-rich atmosphere of the direct cooling zone is prevented from entering the indirect cooling zone via the sealed gate structure thereby permitting frost-resistant bricks to be fired and cooled on a continual basis.