Multiplicity of air exchange - the ratio between the volume of air entering the room and the volume of the room itself. It is usually measured in 1 / h. In other words, this figure shows how many times per unit of time in the room completely air changes.
Why is it necessary? The fact that the cleanliness of the air in the room affects a lot of factors: this is the presence of people or animals, and the number of working equipment, and for industrial premises - and the presence of harmful fumes or other harmful factors. Therefore, if air is contaminated, then it must be changed. Multiplicity of air exchange determines how many times and for how long, usually this hour or, rarely, the daily interval, the air changes. There is also a concept - the ventilation volume, which shows not the ratio, but simply the number of cubic meters of air passing through the room per unit time. Both these quantities are interdependent, but more often use the multiplicity of air exchange.
The most important use she finds in construction, namely - when designing a variety of buildings and structures. The supply and exhaust ventilation systems are developed exclusively on the basis of this value. To ensure that designers do not overwork, they calculate the ventilation of the room. There are specialized standards, in which it is clearly prescribed, what should be the multiplicity of air exchange in the room, depending on its purpose. Everything is painted there: dining rooms, kindergartens, restaurants, factories, steamers and even separately in the rooms, kitchen, bedroom, etc. Engineers take a ready-made figure and on the basis of it develop a ventilation system.
Distinguish the supply and exhaust system, the main one to ensure the required volume of air is considered exhaust. The inflow is often neglected altogether, considering that the air comes through leaks in building structures, windows, doors, cracks in the floor. Air can not come more than it's gone, or vice versa, so the balance of the ventilation volume between them must be maintained. Especially this issue is relevant, when the multiplicity of air exchange in production premises is taken into account. Due to their size and large magnitudes of multiplicity, industrial buildings require a more careful approach to the development of a ventilation system. When the figure of air exchange from five to ten volumes per hour, it is already impossible to do with natural loopholes. Here, powerful supply systems with mechanical impulse, local exhausts, combined recuperative systems come into play ...
The multiplicity of air exchange, being an important figure in construction, does not find its practical application in everyday life. If it is stuffy to us, we open the window, if it's cold, we heat it. But here there is a small nuance. Modern metal-plastic windows and doors, as more hermetic structures, significantly reduce the influx and reduce the quality of air in your home. The author during the energy audits repeatedly observed how in the kindergartens after a quiet hour in the middle of the winter they opened the windows wide open, in order to ventilate the room, for the stuffiness is terrible. To prevent this from happening, you need either to put windows with special adjustable slots, or next to a window in the wall to install a small recuperator.