Aircold Ventilation supplies advanced motorized fire smoke dampers designed for reliable fire and smoke control in HVAC systems. Pressure relief dampers of PRD for the protection of internal spaces from differential pressures in excess of set maximum levels, when the set maximum differential pressure is exceeded, the blades. automatically open to relieve the excess pressure Non-Re... https://aircoldventilation.com/pressure-relief-damper-non-return-damper/