Ventilation boxes - how not to spoil the ventilation in the
Quite often, tenants of apartments in pursuit of an increase in free space in the kitchen or in the bathroom agree to “improve” the ventilation system. As a rule, this is due to the fact that the ventilation boxes are simply partially dismantled, which in the future causes serious problems. In order to prevent this, it makes sense to understand in more detail the purpose and functioning of this element of the ventilation system.

The principle of operation and purpose
In the section in any ventilation duct, 3 channels are visible, while one of them has a much larger area than the other 2.
Each of them plays a role:
- small channels (they are also called satellite channels, the diameter of such ducts in typical houses does not exceed 15 cm) are used to remove air from the bathroom and kitchen;
- grand canal - a common air duct in which the air drawn from different apartments is mixed.
The dimensions of the ventilation ducts in residential buildings are, in principle, comparable - in general, it should fit a large air duct (approximately 30x60 cm) and 2 satellite channels (each 15x15 cm).

It works according to the following scheme:
- air through the ventilation grille is drawn from the restroom and kitchen into the corresponding satellite channel;
- the air does not enter the common shaft immediately, before it passes vertically about 3m. A rectangular plastic ventilation box can be used to supply air from the room to the satellite canal;
- in the mine air is mixed with the hood from other apartments and rushes to the roof, where it is removed beyond the limits of the ventilation system.

Note! The apartment is the main part of the satellite channels of the underlying housing. So the removal or violation of the geometry will hit primarily on the neighbors below, and already they will bring a lot of trouble to you personally.
Read more about the design
Quite often the box for ventilation in the kitchen or bathroom occupies a decent area. Given the eternal lack of free space, many are engaged in undesirable amateur and remove some of the box or reduce its size.
If at the bottom of the neighbors he has enough quick-wittedness to turn to the law enforcement agencies, then with a 100% probability, the unlucky architects will be obliged to restore the destroyed structure. (See also the article Exhaust ventilation at home: features.)

Note! Despite the fact that the box itself is located in the apartment, it is not owned by the residents. So unauthorized change is illegal.
What threatens the dismantling or narrowing of the box
Many so-called experts offer services to reduce the size of the structure without deteriorating the ventilation in the apartment. But they forget to add that as a result of this "modernization" neighbors will suffer from below.
Most often, this simply cuts out part of the box. The price of such a service is relatively small, moreover, due to the removal of part of the design, the free area increases dramatically. You will have to pay for it to the underlying apartments, because of this, an unpleasant smell will begin to penetrate into the rooms.

The fact is that with this method of modernization of the duct the size of the large ventilation duct is sharply narrowed and some of the satellite channels are cut off. As a result, if earlier the air through the satellite channels quietly got into the ventilation shaft, now it rests on the partition at the exit.
In addition, due to the sharp narrowing of the duct area in front of the bottleneck, an area of high pressure is formed, which also does not improve ventilation. As a result, the pipe simply cannot physically work with the same productivity as before, and some of the polluted air flows back into the rooms. To fix the situation can only restore the geometry of the structure, fortunately, these works can be done with your own hands.
Recovery Guide
The main task is to obtain, at the end of the work, the initial dimensions of the ventilation box (before its modification).
Instructions for performing work looks like this:
- removes finishing material from the remaining parts of the structure;
- need to expose the inner space. To do this, it is necessary to remove part of the walls and both floors;

- depending on what material was used for the construction of the box, the material is chosen to tune it;
Note! Before you engage the walls, you need to restore the cut-off part of the satellite channels coming from the underlying apartment. To do this, you can use plastic or metal ducts.
- restoration of the ventilation duct provides for laying out its walls anew. For this, foam blocks or gypsum slabs are most often used - the walls will not be subjected to heavy loads, but excellent workability will only speed up repairs;

- after the box geometry has been restored, it will only be necessary to check its operation (the neighbors should have ventilation at the bottom) and re-trim the walls.

Note! For the internal partition it is not recommended to use thin sheet metal, plywood, etc. In the future this may cause problems with noise, and this deficiency can be corrected only if the walls of the box are removed.
In some cases, it may be necessary to make boxes for ventilation that is called "from scratch" when it was completely demolished. The order of performance of work remains the same, only the volume increases slightly.
Plastic and metal boxes
Quite often there are references to plastic and metal boxes. When applied to ventilation, the definition of plastic boxes for ventilation usually means the section of the duct from the hood to the vent in the wall. Also, such structures can be used to hide an unsightly fragment of a pipe, for example, in the area between the kitchen hood and the ceiling.
Plastic and metal boxes for ventilation are good, first of all, the appearance. As a rule, such designs do not require additional finishing, and with the right approach they can themselves become an interior decoration.

As for the shape of the section, there is no universal solution. Round air ducts in terms of aerodynamics look preferable, and a square (rectangular) cross-section is easier to install due to flat surfaces.
The dimensions of the plastic ventilation duct are selected on the basis of the power of the exhaust, but most often used are sizes such as 204x60 mm, 120x60 mm and 110x55 mm. With a further reduction in the cross section, its productivity will be too small.

Note! The listed sizes of plastic boxes for ventilation have the same height not by chance. Quite often they are masked behind a plasterboard partition, so the section height does not exceed 60 mm.
Get rid of the noise
There can be several reasons for noise:
- unsuccessful alteration of the box;
- use of fans;
- if a corrugated pipeline was used, it could not be stretched strongly enough at the installation stage; as a result, its surface resembles a washboard and the air makes a lot of noise when it touches it.
In any of these cases, you will need insulation insulation of the ventilation duct.
There are several ways to combat noise:
- cover the box with a layer of noise insulation. Such a material can be self-adhesive, in which case it is sufficient to simply glue it over the entire surface of the box;

Note! There is the option of attaching sound insulation to the inner surface of the box, but in this case there is a high probability of dampening of the material and the development of fungus on it.
- if the main source of noise is a fan, then you can reinstall it using antivibration flexible inserts. Or simply replace it with a less noisy one; also, a special installation can be installed behind the fan itself to combat noise;
- lamellar silencer can be used;

- Rigid air ducts can be replaced with flexible ones, air friction on their walls will be significantly reduced, and hence the noise problem will disappear.
In conclusion
Ventilation is a rather fragile system and it is very easy to interfere with its performance by inaccurate intervention. In particular, ventilation boxes are at risk - illiterate work with these system elements leads to unpleasant consequences.
In order to avoid this, it is enough just to adhere to the recommendations proposed in the article. The video in this article shows in stages the process of restoring the ventilation duct.