Because of the great height of modern multi story buildings, it’s often not possible to open windows. To achieve a pleasant living and working climate a ventilating system is often used in such buildings. Due to the size of those buildings large air vents and high air speeds are necessary. This type of ventilation forces fire detection to be placed in the ventilation ducts. Due to the high air speed and the fact that the air is drawn from multiple rooms, smoke created in one room could get diluted extremely. The only reliable fire detection system for such areas is a high sensitive smoke detection aspirating system like Stratos. These systems have been widely used in the past years.