Air Control Products: HHE/NRD
AirVent family →When a fan stops, the duct becomes a shortcut for reverse flow unless something closes it. An NRD's counterbalanced blades swing open on airflow and fall shut under gravity the moment it stops: passive, reliable backflow prevention at fan discharge.
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When a fan stops, the duct becomes a shortcut for reverse flow. NRD blades swing open on airflow and fall shut under gravity the moment it stops: no springs, no power, no backflow.
More from Dampers
Manual or motorized multi-blade dampers for balancing air volume across supply and return mains: the tap of the duct system.
Aerofoil-blade VCDs: shaped blades that throttle high-airflow mains with less noise and turbulence than flat blades.
Round VCDs: single-blade volume control for round ducts, spigots and branch take-offs.
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