Air and thermal-air curtains are designed to protect the gates and open entrances of industrial buildings from the intake of cold air in winter. There are two types of curtains: sliding, in which a flat jet of air is supplied either from below or from the sides of entrances and gates at some angle towards cold air, and mixing, when air from the building is supplied to the vestibule between the double entrance doors. Mixing curtains are used in administrative and public buildings, in passageways, etc. Curtains in which the air is preheated in an air heater are called thermal-air, and curtains that supply air without heating are simply air type.

Air-heating units with full or partial air recirculation are often used in air heating systems.

General exchange exhaust ventilation systems usually remove air from the upper, less often from the middle zone of buildings. Before removal, the air in general exchange exhaust systems usually does not undergo cleaning. General exchange exhaust systems can be channelless if the air is removed by roof fans that are installed on the floors, and ducted. In ducted exhaust ventilation systems, air is sucked into air intake apertures or grilles, it is fed through the ducts to the fan and, after passing the exhaust shaft, enters the atmosphere. To protect the exhaust shaft from atmospheric precipitation, an umbrella is installed above it, and the air ducts are blocked with a flap when the fan is not working.

Local exhaust ventilation systems are designed to take harmful emissions from the places of their formation with the help of shelters or local suction, transport polluted air, clean it in filters or dust collectors and release it into the atmosphere. Local suction and shelters have the most diverse design and shape: these are umbrellas, fume hoods, full shelters, side and ring suction at baths and shaft furnaces, suction panels, casings, etc.

Many harmful substances released during technological processes actively affect local suction pipes, air ducts, fans, filters, causing their severe corrosion, in addition, they can be explosive and fire-hazardous. In these cases, air ducts and other devices in contact with an aggressive environment are made of materials that are not subject to intense corrosion by the moving medium (corrosion-resistant alloy steels, aluminum, titanium. metal, vinyl, polyethylene, etc.), or apply special coatings of steel ducts with acid- and alkali-resistant dyes, enamels and varnishes. In such systems, fans and other equipment are installed in an intrinsically safe protected design.

1. Name the main parameters of the air environment.

2. What is the main purpose of the ventilation system?

3. In which cases the use of natural ventilation systems is justified.

4. What is the advantage of mechanical ventilation systems?

5. What is the name of the process of heat recovery of the removed air, what are its technical and economic advantages?

6. What material is used to produce ventilation ducts most often?

7. What, in your opinion, is affected by the thickness of the metal in the production of air ducts?

8. In which cases air showering is used?

9. Name the main processes of air treatment in the supply ventilation system.

10. In which cases a special design of air ducts and ventilation equipment is used?

As indicated above, the required state of the air environment in the premises is maintained by general exchange ventilation methods by pumping clean ventilation air into the premises with the necessary temperature-humidity parameters and removal of air that does not meet regulatory requirements. In accordance with this, general exchange ventilation systems should include equipment and devices for intake of outdoor air, its processing, transportation and distribution around the premises, as well as for the removal of exhaust air.

These include air intake and air discharge devices in mechanical ventilation systems, which are made in the form of holes in the fences of buildings, attached or freestanding shafts. When air is taken from above, the air intake devices are placed in the attic or upper floor of the building, and the channels are removed above the roof in the form of shafts.

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).