Air transfer vent grille designed for use in fire resisting doorsets and compartment walls. When dormant, the grilles allow air to circulate throughout the building. In the event of a fire they are designed to close and restrict the flow of hot gasses and fire. Matching face plate cover available (CLBES423) sold separately. All air transfer grille systems are tested to BS476 part 20/part22:1987 - 30 and 60 minute fire rated. Comes with a 10 year mechanical guarantee. Suitable for all domestic, commercial and industrial use.