The DA-VxVSN Series Galvanized Steel Blade & Frame Class III Dampers are designed to control the flow of air in Heating, Ventilating, and Air Conditioning (HVAC) systems, and to meet different application and environmental requirements. The DA-VxVSN Series dampers are tested at an Air Movement Control Association (AMCA) Certified Laboratory using instrumentation and procedures in accordance with AMCA Standard No. 500, Test Methods for Louvers, Dampers, and Shutters. DA-VxVSN Series Dampers with seals rated for Class III leakage resistance are suitable for applications where tight closure is not required, such as return air applications. Do not use DA-VxVSN Series Dampers for outdoor air applications.