For return air in habitable rooms directing the air sideways to prevent occupant discomfort. The pre-fitted intumescent gasket material in a fire situation will rapidly expand to seal off the open air valve.The penetration is then sealed against the spread of fire and the fire rating of the ceiling construction is maintained. Range comes in 5 sizes (80, 100, 125, 150, and 200mm) Meets the requirements of Building Regulations Document B Maintains the integrity of Fire Rated ceilings for up to 60 minutes Includes intumescent gasket Available ex-stock