Nat Vent FD100 Twin Blade Fire DAer. 100mm In-line. Monsoon is the brand name for National Ventilation's products, a name that is well-known and trusted by architects, consultants, specifiers, wholesalers, contractors, and installers for over a decade. Continued research and development have led to an expanded range of Monsoon energy-efficient ventilation solutions, including mechanical ventilation with heat recovery (MVHR), single-room heat recovery (SRHVR), mechanical extract ventilation (MEV), decentralised mechanical extract ventilation (dMEV), and intermittent extract ventilation (IEV). It functions as a fire backdraft prevention shutter, effectively blocking airflow into potential fire hazards. Colour/Finish: Mixed