Back draft shutter

When your extraction system is turned off a back draft shutter is the perfect way to stop air escaping from your room. It will also prevent unwanted cold/hot air from coming back into the grow room when it is not wanted.  A Backdraft shutter is a cylinder-shaped piece of equipment with 2 centrally mounted flaps. The air produced by your duct fan will cause these flaps to open, however when the duct fan is turned off the flaps will shut meaning no air can come in from outside.