For aeration, air intake and ejection devices are made in the form of rotating transoms, opening lanterns, windows or other overlapping apertures in the fences of buildings.

The location and design of the air intake devices are selected taking into account the cleanliness of the intake air and the satisfaction of architectural requirements. Thus, air intake devices should not be located near sources of air pollution (emissions of polluted air or gases, chimneys, kitchens, unpaved roads, etc.).

Air intake apertures should be located at a height of at least 2 m from the ground surface and closed with louvered grilles (in the green zone – at a height of at least 1 m).

To protect the premises from outside cold air during standby of the ventilation through ventilation ducts, air intake and air discharge devices are equipped with multi-leaf insulated valves with manual or mechanical drive. In the latter case, the valve is blocked along with the fan closing the apertures. At low temperature of the outside air, the valves are supplied with an electric heating system in order to protect their flaps from freezing. Electric heating is turned on for 10–15 minutes before starting the fan (Fig.2).

Fig.2. Electric air valve

The outer walls of exhaust ducts and shafts are insulated to avoid condensation and ice of water vapor from the extracted moist air. The air velocity in the supply channels and shafts is supported between 2 and 5 m/s, in the channels and shafts of exhaust devices: 4–8 m/s, but not less than 0.5 m/s, including for natural ventilation.

The main ventilation equipment of supply and exhaust installations, as a rule, is installed in special rooms called ventilation chambers. Supply chambers in public, administrative, residential buildings are usually designed on the ground floor or in the technical underground. Exhaust chambers should be located in the upper part of the building. In multi-storey buildings with a large number of ventilation systems, ventilation chambers are arranged in technical floors.

In buildings with a large number of ventilation systems (more than 5), a room for equipment repair is provided. The operation of ventilation systems is controlled from special remote controls using automation and remote control devices.

The fan is a mechanical device designed to move air through the ducts of ventilation systems, as well as to carry out direct air supply to the room or suction from the room, and creating the pressure drop necessary for this (at the inlet and outlet fan). According to the design and principle of operation, fans are divided into:), radial (centrifugal), diametral (tangential) (Fig.3).

Fig.3.Fan designs

Currently, modifications of radial fans are used – direct-flow, disk, vortex, tornado (Fig.4).

Fig.4. Modifications of radial fans

Fans are evaluated by specific speed, which relates the rotational speed and pressure.

We divide fans into three groups, depending on the magnitude of the total air pressure they create: low pressure (up to 1 kPa), the maximum circumferential speed of such wheels does not exceed 50 m/s; medium pressure (up to 3 kPa), the maximum circumferential speed reaches 80 m/s; high pressure (up to 12 kPa), the circumferential speed of the impellers is more than 80 m/s.

The separation of fans by pressure is conditional, since any high-pressure fan with a decrease in the speed of rotation can be used as a medium-pressure fan.

In the direction of rotation of the impeller (when viewed from the suction side), the fans can be of right rotation (the wheel rotates clockwise) and left rotation (the wheel rotates counterclockwise).