Air Distribution Products for Operating & Procedure Rooms Greenheck's new line of healthcare, laboratory, and cleanroom (HLC) air distribution products are designed, engineered, and tested to meet or exceed today's critical environment standards for performance and energy efficiency. Structural Modular Plenum Arrays Specify with confidence. Specify Greenheck. Modular Plenum Arrays Heavy-Duty Suspended Ceilings Laminar Flow Diffusers VIEW CATALOG