Height: 225 mm Width: 225 mm Thickness: 40 mm features: Intumescent material formed into square, rectangular or circular matrix and contained within a steel frame On exposure to heat from a fire the intumescent material swells to produce a fire resistant seal against the passage of fire, smoke and hot gases The grilles are easily installed in vertical apertures in doors, walls and ducting Tested to BS 476 Part 20/22 Up to 1 hour fire resistance High free air flow in either direction Free air space 32,700 sq mm Easy to install can be used with 51095 face plates Available in a range of sizes to order