Suspended ceilings consist of a metal grid supporting acoustic tiles. This system provides sound absorption, easy access to mechanical systems above, and a finished interior surface. Main runners (primary support members) are suspended from structure above. Runners typically span 12 feet between suspension points. Hangers and wires support runners. Spacing of hangers prevents sagging. Cross-tees fit into main runners at 4-foot intervals. Cross-tees support tiles and transfer loads to main runners. Acoustic tiles rest on the grid without fastening. Tiles are removable for access to utilities above. Ceiling height is determined by building design and aesthetic preference. Lower ceilings enclose space but may feel cramped. Higher ceilings provide openness but increase HVAC costs. Light fixtures, smoke detectors, and air vents are built into the ceiling. Coordination with trades is necessary for proper placement. Accessibility of systems above is maintained through removable tiles. Return air plenums above ceilings return air to HVAC systems. Proper sealing prevents air bypass. Acoustic performance measured as noise reduction coefficient (NRC) indicates absorption. Higher NRC values absorb more sound. Grid supports and tile selection affect final NRC rating.