Two types of passive window ventilation are offered – the Vented Sash and the Window Vent. These let fresh air trickle into a room when the windows are closed. This is a safe way of airing rooms, particularly when they are closed for long periods. Continuous background ventilation reduces condensation, mildew and dust mites. Both the Vented Sash and the Window Vent are unobtrusive ‘add-ons’ to standard joinery and let users control the level of air entering a room, in that they can be closed if desired. The First Window Vent is fitted above sashes or fixed windows while the First Vented Sash is placed at sill level.