The Filter Fan Unit 1200x600 (0.0.716.42) is placed onto the Fixing System, Angle Strip X 8 that is fastened to the ceiling construction and is not screwed into place. The half-round polyurethane gasket of the HEPA Filter (0.0.712.76) creates an airtight seal so that only filtered air can get into the working area. To protect its high filter performance, the HEPA Filter must be handled with extra care during transport and installation.