The ceiling tile, in one embodiment of the invention, is a laminate of a rigid core layer, such as gypsum, having one surface covered by a display layer of plastic sheet material. An opposite surface of the core layer is covered by a layer of light reflective material. The design layer has a design surface that is viewable when the tile is installed in a ceiling, and the light reflective layer has an exposed light reflective surface. Both the design layer and the light reflective layer form leak tight seals on the opposite surfaces of the rigid core layer. The entire peripheral edge of the tile laminate and marginal portions of the design surface and light reflective surface are covered by a plastic leak tight tape that forms a gas tight seal at the peripheral edge of the tile laminate.