Ventilation - air removal from the premises and its replacement outer clean air. Ventilation is provided by a state of air in premises in accordance with hygiene requirements. In residential and public buildings, the livelihoods of people, processes of life (cooking, washing clothes, etc.,) are accompanied by a decrease in the concentrations of oxygen, the accumulation of carbonic acid, heat and flagovedeniya and air pollution, premises and evil-smelling substances and cause the need of permanent or periodical replace it with fresh. The intensity of such replacement taken to determine the attitude of the watch volume replaceable air to volume of space, i.e. the ratio of exchange per hour. In accordance with the hygiene requirements established norms multiplicity of exchange for housing, children's, school and hospital buildings (see table).
Ventilation of industrial premises is an important means of combating the discharge of harmful gases, vapours, dust, excess heat and moisture. The sources of these selections are the technological processes, production equipment and people. However, this fight must begin with activities that prevent or reduce the specified selection (locating the source of unfavourable selections by shelters with suction air - local pumps). Nonlocalized selection is removed with the help of ventilation. Adequate ventilation is determined by the formula:
where g is the hour number of escaping into the air space of harmful substances in mg/HR; CPD - maximum permissible concentration of harmful substances (MPC) and CP. - concentration of this substance in the input air in mg/m3.
The ventilation air in the living and some public areas Uosukainen (sanitary norms ventilation)
The air in the premises is carried out in different ways: 1) natural ventilation through Windows, doors, pores in the walls, due to the difference between the pressure of the air inside and outside; 2) artificial ventilation - with the help of mechanical devices.
The efficiency of natural ventilation depends on the area of air vents, transoms (which shall be not less than 1/40 floor space), the temperature difference between indoor and outdoor air, the degree of porosity of the walls.
Artificial ventilation provides a constant exchange of air in the room. It happens exhaust, intake and supply-and-exhaust and is carried out by means of axial and centrifugal fans (Fig. 1 and 2).

axial fans and centrifugal
Fig. 1. Axial fan: 1 - wheel with blades; 2 - cover.

Fig. 2. Centrifugal fan: 1 - casing; 2 - frame; 3 - outlet; 4 - intake.
installation for air conditioning
Fig. 3. Installation for air conditioning: 1 - hole for the incoming outdoor air; 2 - mixing chamber; 3 - spray chamber; 4 - camera with separators for delay drops of water; 5 - centrifugal fan; 6 - pump to supply water; 7 - heater; 8 - intermediate Luggage.

Exhaust system consists of a fan with motor and air ducts. Air of industrial premises, polluted by dust, harmful gases or vapors, before release to the outside must be cleaned. Supply air to create a favorable climate (see) in the premises of the preliminary process. Therefore, in the supply system, in addition to fans, electric motors and channels, are heaters (radiators), filters or paleostomi camera, humidifying or washing chambers, refrigerating and drying installation. When there is a need to maintain the premises in the conditions of constant temperature and relative humidity, used devices for so-called air-conditioning (Fig. 3).
Sanitary norms in the USSR, related to devices ventilation, are concentrated in the following documents: Sanitary norms of planning industrial enterprises CH-245-63 (section 4B); Construction norms and regulations SNiP II-G 7.62 self "heating, ventilation and air conditioning"; design Standards, construction norms and regulations II-M. 3-68 "Auxiliary buildings and facilities of industrial enterprises".
The task of the sanitary control (preventive and current), largely carried out by employees of epidemiological stations (SES), which includes verification of compliance with the main provisions of these documents.
When checking ventilation should pay attention to the correctness of its use, namely that not only extraction, but also supply; submitted to the supply air is not created unpleasant blast; to microclimate conditions corresponded permissible, and in selected air samples do not contain harmful substances above the MPC. If the control should use the psychrometers, anemometers, check boxes, and artificial fog. To control air pollution should be involved in the chemical laboratory facilities or businesses.