Repair of ventilation systems: analysis of popular malfunctions and methods for their elimination

Alexey Dedyulin
Checked by a specialist: Alexey Dedyulin
Author: Alina Zlobina
Last update: April 2019

Air handling units update the air, remove harmful components from a confined space, maintain a comfortable microclimate. Without good air exchange in the room there is a risk to the health of all households. A threatening situation occurs when the ventilation system is malfunctioning.

We will tell you about how to get rid of stagnant air, which provokes problems with the respiratory system, exacerbating chronic diseases. In our article, we describe in detail the ways in which ventilation systems are repaired. Tips for restoring and maintaining them are provided.

Ventilation options

When repairing a system, you need to understand how it works and by what principles it works. Distinguish between natural and forced type of ventilation.

Features of natural air exchange

All old buildings are equipped with exhaust ventilation systems of a natural type. Air flows in them, obeying the laws of physics. They enter through the windows, cracks in the windows and doors, move through exhaust ducts connected to the common route and exit through openings in the pipe on the roof of the building.

Natural ventilation is not expensive and easy to maintain, since it lacks mechanical equipment. But there are significant shortcomings - it responds to weather changes, does not work well in the summer and does not provide an opportunity to control air exchange.

The principle of natural ventilation
The movement of air flows in natural ventilation occurs due to gravitational forces: temperature differences, air column pressures, wind. To enhance the outflow, deflectors are installed at the pipe outlet to improve circulation.

The principles of forced ventilation

In modern construction, heat-saving technologies are used, providing for the complete tightness of housing. Such conditions provide a comfortable stay, but prevent the natural flow of air into the room.

Therefore, new homes are equipped with forced or mixed ventilation. Here, the movement of flows is carried out mechanically using a fan. The supply pipe is located at the bottom of the building, and from it, air ducts are connected to the apartments, connected to a common route.

Ventilation consists of a set of devices that contribute to the removal of air over significant distances:

  1. Ventilation ducts. Flexible and rigid pipelines made of plastic, galvanized sheet or aluminum foil, combined into one network by tees, turns and adapters. Provide air supply to isolated rooms.
  2. Fans. Axial and centrifugal devices with a paddle wheel. Gaseous mass is fed and removed, creating the desired pressure in the system.
  3. Intake grille. Passes external air flows, protects equipment from precipitation and foreign objects.
  4. Air valve. Prevents external air from entering the room when the system is turned off.
  5. Filters. Protect ventilated space and equipment from dust, debris, insects.

The forced system is not affected by temperature fluctuations and pressure in the chimney. Its effectiveness depends only on the performance and power of the fan.

The principle of operation of forced ventilation
The forced ventilation system constantly replaces the exhaust air, and if necessary warms it up

However, it is worth considering that such a device consumes a lot of electricity and needs regular maintenance. In the event of a breakdown, the repair of forced ventilation systems can "fly into a pretty penny."

The schemes of ventilation systems used in the arrangement of apartment buildings are described in detail in the next article, the contents of which we advise you to read.

Threats to air exchange

Disruptions in the performance of ventilation ducts are not immediately noticeable, but sooner or later result in unpleasant consequences.

The following symptoms indicate a malfunction of any type of air exchange:

  • the smell of charms and rot appeared in the house;
  • mold and fungus began to multiply actively, both in hard-to-reach places behind cabinets, a kitchen sink or a table, and in open areas;
  • condensation constantly forms on the surfaces of windows, walls and furniture;
  • it becomes damp, cool in the room, the oxygen supply is not replenished, it is difficult to breathe;
  • the system makes a hum and loud noises, which causes discomfort;
  • the smell of burning is heard from the ducts.

The safe operation of solid fuel units and the quality of ventilation depend on gas heating equipment. Ventilation ducts are brought out and do not allow harmful combustion products to accumulate in the room.

Condensation and mold on the windows - a sign of a malfunction in ventilation
If the windows have to wipe mold and condensation every day, then most likely the air ducts can not cope with their tasks. This means that it's time to think about repair and maintenance of the ventilation system.

If at least one of the signs of a malfunction appears, you should immediately begin to diagnose, identify and eliminate the causes of breakdowns in the system.

How to check system performance?

The easiest way check the air exchange in the apartment or in a house - open a window in one of the rooms and bring a thin sheet of paper to the ventilation. With normal traction, it will stay on the grill. Such a check is quite approximate.

Fire isn't the best way to test ventilation.
It is undesirable to conduct testing using matches or candles. Gas can be present in the channels, and even its minimal amount can provoke an explosion or fire

The calculation tables and the anemometer, a special device that measures the speed of air movement, can more accurately determine the system’s performance. After measurements, the table contains the values ​​of the device and the parameters of the hole section. The result is a figure showing the amount of air passing through the mine in an hour.

Anemometer - a device for checking the speed of air movement
The anemometer quickly measures the speed of the air-conditioning treatment object in the ventilation shafts and makes it possible to accurately assess the quality of the ventilation equipment

Normal values ​​of air circulation in the apartment:

  • kitchen - 60 m³ / h;
  • bathroom and toilet - 25 m³ / h.

When there is a real velocity of the gas flow, it can be used to determine the volume. No additional tables or directories are needed for this.

The volume of air flow is calculated without tables using a simple formula:

Q = V x S x 360,


  • S is the cross-sectional area of ​​the hole;
  • V is the reading taken from the anemometer.

It turns out that at a speed of 22 m³ / h and a cross-sectional area of ​​110 mm, the amount of transmitted gases will be equal to: 22x110x360 = 871.2 m³.

Basic faults and solutions

Ventilation systems fail for various reasons. Often this is incorrect installation and operation, neglect of maintenance, the appearance of mechanical damage and corrosion processes, the natural wear of parts and devices. All of them are fraught with typical malfunctions. Let's consider them in more detail.

The most common problem is insufficient airflow in rooms with natural ventilation. Its reason lies in the high tightness of the premises.

The natural system is designed for air flow from doors, wooden windows and other cracks, which we try to carefully eliminate during the repair. Sealed plastic windows, unlike old wooden counterparts, do not allow air to pass through, blocking all the possibilities for its normal circulation.

The same applies to doors that impede its movement between rooms. Because of this, condensation and mold stains constantly accumulate on the windows.

Air inlet valve for plastic window
Air passage valves “depressurize” the room exactly as much as the conditions required for normal operation of natural ventilation. They will not affect the room temperature in any way

The way to solve the problem is this: cut small holes in the doors by installing grilles or decorative bushings in them. And also arrange regular through ventilation, install valves with microcirculation on windows or walls.

The hinged valve for the window is fixed with short self-tapping screws on the sash inflow. Supply wall device mounted by drilling the opening and attaching the housing with sealant.

Another problem is a difficult hood. Its cause may be a garbage congestion in the channel, as well as insufficient power or compressor failure.

To fix this, you will need to clean the air ducts, replace / repair the compressor. The new device must carry out air exchange in a volume of at least 3 cubic meters per hour for each square of the area of ​​the room.

The appearance of unpleasant odors from the ventilation duct causes leaks in the duct, corrosion processes, violation of the integrity of the parts.

Way to get rid of the problem: replace damaged soft inserts, wafer seals, repair or replace sections and elements of the duct with defects. And also adjust the tightness of the joints.

A problem such as a significant deterioration in air quality and increased resistance of ventilation ducts may occur. Its reason lies in the accumulation of contaminants in the duct, the low efficiency of the filters.

Remedy is to clean as much as possible. ventilation duct from debris, wash and dry the filters or replace them with new ones.

Replacing the ventilation grill
Everyone can replace worn and excessively dirty filters. Thus, high resistance is removed and air circulation through the channels is established.

The appearance of loud noise from the air ducts is associated with the penetration of insects, birds, small rodents into the pipeline, insufficient lubrication of the moving parts of the equipment, and strong winds.

To get rid of the problem, it is necessary to attach a protective mesh to the inlet / outlet ducts with screws, regularly lubricate the mechanisms, wrap the pipe with soundproofing material, install silencers.

Repair of the ventilation system by specialists
If it is necessary to replace individual parts and carry out major repairs of ventilation, an experienced specialist cannot do without it. Otherwise, there is a risk of more harm than fix.

On its own, it is recommended to carry out only routine repairs of ventilation systems, which does not provide for significant interference in the design and complex dismantling. For example, noise insulation or ventilation duct cleaning. In most cases, this is enough to fix the main problems.

System Noise Reduction Techniques

Fans, valves, air pipes and forced ventilation flaps produce certain sound vibrations that can be heard indoors. According to sanitary and construction standards, the noise level should not exceed 30-40 dB. A violation of the norms is signaled by chronic fatigue, headaches and other health problems.

The noise that occurs during operation is either aerodynamic or mechanical. In the first case, it appears due to poor depreciation, poor condition of the nodes, friction and violation of the balancing parameters. In the second, it is the result of the operation of electric motors and fans.

The following measures will help reduce the noise of the ventilation system:

  • installation of the fan on vibration isolating bases;
  • careful adjustment of parts and balancing of rotating parts;
  • strong fixing of the fan, valves and gate valves;
  • installation of a removable soundproof casing;
  • the insertion of rubber or tarpaulin gaskets between the fan and the duct;
  • lining the inner surfaces of the ducts with materials that absorb sound (fiberglass, mineral felt);
  • lubrication of moving parts of the compressor.

In ventilation of a natural type, the noise is very noticeable in windy weather, since getting into the system at high speed, the wind creates a strong hum. A chamber, plate or tubular silencer can cope with it, which reduces the sound pressure on the walls. It is installed at the top of the chimney.

Mineral wool for air duct
Mineral wool from verified manufacturers in rolls 5 cm thick is suitable for noise insulation of ventilation ducts. The insulation will not only absorb sound, but will also maintain optimal air temperature, prevent condensation and protect the structure from fires

Another way to dampen vibration is to equip a concrete frame around the roof duct. If technical reasons do not allow such an operation, the channel is wrapped with insulation.

Cleaning Instruction

Dust, small debris and cooking oil, which constantly accumulate in the ventilation ducts, cause numerous breakdowns and poor-quality system operation. Undesirable effects can be prevented by scheduled cleaning in the system every 3-6 months.

When starting cleaning the duct, it is advisable to follow a certain procedure:

  1. Wear tight protective gloves and a mask, prepare a working stable ladder or chair.
  2. Remove all ventilation grilles, wash them with detergent, and then rinse thoroughly. If they are badly worn, replace them with new ones.
  3. To clean the inside walls of dirty crusts with a small construction spatula (plastic, wooden or rubber), making sure that it does not deform or damage the channel.
  4. Vacuum the hole in accessible places and wipe with a damp sponge.

AT forced system instead of a grate, an exhaust fan is located in a niche. It is first turned off and carefully removed, unscrewing the screws that secure the case. Then wash the blades and the grill with a special tool that breaks down the fat, and wipe it dry.

To fully restore normal air circulation, you need to try to clean the channel as deep as possible using an improvised tool. It is necessary to move carefully, with gradual rotational movements.

At the end of the work, a traction check is carried out with an anemometer or a piece of paper.

Manual ventilation cleaning tool
It’s easy to make a tool for cleaning ventilation ducts. A strong and long steel cable will do for this. To it you need to attach an ordinary brush and a small load

It should be remembered that residents of apartment buildings are not allowed access to the main mines. Therefore, if cleaning part of the channels inside the apartment did not solve the problem, it makes sense to call special services.

They perform efficient large-scale processing with a vacuum cleaner and a brush machine, and disinfect the inner surfaces of pipes with chemicals.

Air duct contamination
Air vents become clogged quickly. During cleaning, a lot of waste can be strewed from them, up to the remains of rodents and insects. The floor surface under the vents should be freed from furniture in advance and covered with newspapers or film.

You can disinfect the channels yourself by preparing an inexpensive universal solution of chlorhexidine, boric acid, fir oil and alcohol. The ingredients are placed in the atomizer, which is used to process the walls of the ducts.

Disinfection treatment will eliminate allergenic factors, neutralize all microbes and bacteria living in the pipes. It must be carried out at regular intervals immediately after cleaning the exhaust ducts.

How to improve ventilation performance?

Any breakage is always easier to prevent than to fix. This will save energy and money on calling the master and buying new equipment to replace the broken one.

Simple preventative measures will help:

  • checking the draft force of ventilation;
  • maintaining the cleanliness of ventilation grilles;
  • visual inspection of air ducts, fixtures, equipment;
  • lubrication of movable mechanisms, fan cleaning;
  • airing of rooms.

The main condition is the regularity of these events. For example, the quality of the traction force is checked annually, the channels and equipment are cleaned as they become dirty, and a visual inspection is necessary every few months.

Useful video on the topic

Video # 1. How to independently check the operation of ventilation shafts:

Video # 2. What to do if ventilation works poorly:

Video # 3. Instructions for arranging soundproofing ventilation duct:

Ventilation is the most important engineering network of the building, which has significant functions. Paying enough attention to prevention, you can save the system from global breakdowns and get by with current repairs, easily coping without the participation of specialists.

Tell us about how the ventilation system was repaired in your house / apartment. Share information that will be useful in practice with site visitors. Please write comments in the block below, ask questions, post photos on the topic.

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