According to the material used for the manufacture of air ducts, they are divided into several groups:

1. Folded air ducts made of thin-sheet galvanized steel, up to 1 mm thick (without painting).

2. Folding air ducts made of thin-sheet black steel, up to 1 mm thick (with subsequent painting inside and outside).

3. Welded air ducts made of sheet steel, 1.2- 3.0 mm thick (with subsequent painting with primer).

4. Seam and welded air ducts made of corrosion–resistant steel, thickness from 0.5 mm to 3 mm (usually grades X18N9T) – without painting.

5. Folding air ducts made of titanium (ρ = 4,500 kg/m3), which have the highest corrosion resistance when moving an aggressive medium.

6. Folding ducts made of metal plastic, clad on one or both sides with PVC or PVC film. With a one-sided coating, the film must be inside the duct, in contact with an aggressive environment.

The connection of individual parts of round air ducts to each other is performed by flanging bandages (with a diameter of up to 800 mm) or on flanges made of angular steel (with large diameters).

The connection of rectangular air ducts with a side less than 1600 mm is performed on profiled tires fastened with 4 bolts at the corners. If the side dimensions exceed 1600 mm, additional latches are used.

For conventional general exchange systems, it is preferable to use folded air ducts made of galvanized steel. Welded air ducts are installed with increased density requirements (smoke extraction shafts, air ducts passing through rooms with explosion hazard category A and B) and air movement with a temperature above 80 °C.

Flexible reinforced air ducts are widely used to avoid difficult fitting when connecting from mains to air distributors and grilles.

One of the latest solutions in the field of air distribution is textile air ducts. They are inflated by the flow of air and evenly distribute it along their entire length. In addition to noise reduction, textile ducts have the ability to trap all dust particles larger than 5 microns. They can be used in rooms with a high frequency of air exchange, without creating local areas with increased air mobility, as is the case with jet distribution.

This type of duct combines two devices – the duct itself and the air distributor.

There are several options for the operation of a textile duct. The air supply to the room can be carried out through its entire surface (in this case, airtight fabric channels made of 100% polyester are used) or through special holes made in the duct material (an impermeable fabric with perforated injector holes is used). Mixed versions are also used. The air flow velocity inside the airtight material does not exceed 0.01–0.5 m/sec, the air velocity coming out of the cracks is 4–10 m/sec, through perforated holes (injectors) is 7–13 m/sec.

Cylindrical fabric ducts are the most common. They are convenient if you need to provide intensive air exchange, preventing drafts. Semicircular air ducts are used in rooms with low ceilings, for example, in catering establishments, non-food stores, hotels, etc. Air ducts in a quarter-section of a circle can also be used, installed around the perimeter of the room.

Installation of steel ducts in rooms with high ceilings is quite laborious and time-consuming. The use of textile air ducts greatly facilitates the work. Sections of air ducts (usually 5 m long) are connected to each other with the help of zippers. The air ducts are suspended using stretched cables or rails. In the latter case, the fastening is more rigid, and the duct retains its shape even without air supply. When condensation occurs, a nutrient medium is formed that promotes the development of microorganisms. Textile ducts can be easily dismantled, washed or cleaned. They are produced with a diameter of 100 to 1000 mm and a length of up to 100 m, as well as various densities that allow changing the air supply from 160 to 500 m