The Helios HDH 180 is a horizontal roof ventilation cowl designed to cover convection exhausts and supply air openings on rooftops. Its construction mirrors the design of Helios horizontal outlet roof fans (RD series), ensuring a consistent architectural appearance. Ideal for natural and mechanical ventilation systems, the HDH 180 helps protect openings from the elements. When used in mechanical ventilation setups, flow resistance should be factored into system design using the relevant performance diagrams.