An air grate for a raised floor includes a top plate with apertures for air flow, and reinforcement ribs for structural support. Pairs of ribs include edge flanges that define a horizontal track. Two flat dampener panels temporarily flex to slip between the edge flanges for assembly and then unflex for adjustable movement along the track between different overlapping positions for controlled air flow. The top plate includes corner-forming sections and leveling legs for height adjustment. Foot-print-expanding brackets engage the leveling legs for extending their foot print outwardly so that the air grate can be used on different raised floor systems without misalignment problems with stanchion supports. A handle is pivotally mounted in the top plate between a flush position and a raised position for grasping to lift the air grate, the handle having apertures matching the pattern of the top plate.