Since people today spend much of their time in buildings, a great emphasis is put on the quality of the ambient air. For ventilation are mostly used ventilation systems that brings fresh air into the interior and provide internal exhaust stale air with high humidity, odours and fumes. But most ventilation systems operate on the basis of a timing control. This means that ventilation is set at a constant power. It is ventilation with exchange of a given quantity of cubic meters of air per hour, regardless of the actual number of people in the ventilated area. Simply said – in some cases, there is a poor ventilation and conversely sometimes is we ventilate even it is not necessary. From an energy and economic point of view it is a very inefficient solution.
Ventilation systems use because of the energy-saving reasons, so called recirculation, when a large part of the internal air is mixed with the outdoor one and then it is heated or cooled. The result is a poor indoor air quality.
An essential part of all public buildings, especially in developed western countries (e.g. in France, this regulation is stipulated by law) are the air quality sensors, which are also widely used in households. The most frequent reasons for their use are energy and economic benefits – the sensors precisely regulate the ventilation, which is a big advantage in public buildings with a variable number of people inside. They also serve to detect smoke from cigarettes, cooking fumes in restaurants and are used in production processes.