Sway bracing is required for all ceiling-mounted systems that use drop rods. Sway bracing resists lateral forces, reduces lateral stresses on drop rods, prevents system hardware from loosening, and prevents wear due to cyclic loading. Sway bracing is required at each end of the system in both directions (laterally and longitudinally), and minimum pipe diameter is one inch for systems with drop rods. Flush-mount applications do not require bracing.