A Backblast Damper or Backdraft Damper is a passive isolation device used to prevent a deflagration from propagating back upstream in ductwork in the event of a dust collector explosion. It is usually installed on the ductwork upstream of a dust collector.
The Backblast Damper contains a gate that is held open by the normal process airflow. Should a pressure wave from an explosion in the collector propagate through the ductwork in the reverse direction of the normal airflow, it will force the blade down to prevent the deflagration from passing further upstream.
These dampers can be equipped with an explosion vent or hatch used to relieve the pressure at that point. Dampers without vents can be used in applications where the dust collector is properly vented.