Dampers control the flow of air in an HVAC or combustion system by opening and closing blades. They can be manually activated or controlled using electric motors or air pressure. Control dampers block or allow air to flow through specific sections or components of an HVAC system. Balancing dampers direct and regulate airflow in an HVAC system to help balance system pressure. Backdraft dampers, bypass dampers, and barometric dampers operate automatically when specific pressure conditions occur in the duct. Fire and smoke dampers activate when a fire is present to help prevent its spread through the HVAC ducts.