Description
The blades close when there is no pressure pushing from behind, preventing backflow. As soon as the pressure increases the louvres open to release exhaust fumes, allowing for fresh air intake or any surplus pressure. These are most commonly used for large extraction fans or pressurized rooms.
Weather Louvre
Strip Grilles
Return Air (RA, RARB & RASB)
Egg Crate (Aluminium & Plastic)
Baby Linear Diffuser
Volume Control Damper 



