Low-cost fire-rated ceiling valve
VentWise and Tenmat have developed a fire-rated ceiling ventilation valve to prevent the passage of smoke and fire and which is said to be significantly cheaper than other products. The Firefly valve has been tested to BS 476 and rated for 60 minutes.
These valves use an intumescent material to seal the valve in the event of fire, as shown by these before-and-after pictures.