Setting requirements and key points

There are specific requirements and specifications for the installation of smoke control system in underground buildings in China. The general smoke control system of underground buildings mainly includes mechanical air supply, natural air exhaust and mechanical smoke exhaust. At the same time, the use of combustible materials should be controlled or reduced in the process of room decoration of underground buildings. Fire prevention and smoke prevention are effectively divided or adjusted to effectively control and prevent the smoke emission or diffusion of underground buildings.

In addition, the area of underground buildings in China is >: 50 square meters, and mechanical smoke exhaust infrastructure should be set up for rooms with more combustible substances and rooms with too many people staying in underground buildings. In addition, according to GB500 16-20 14 Code for Fire Protection Design of Buildings (hereinafter referred to as "Building Code"), if there is no natural smoke exhaust in underground buildings, the underground building area is >: 200m2, or the area of a room >; 50 square meters, generally equipped with mechanical smoke exhaust infrastructure. For underground buildings that meet the requirements of natural smoke extraction, but the underground space is relatively closed, a mechanical smoke control and extraction system should be set up.

The main points of smoke control and exhaust system for underground buildings are as follows:

1. Settings of air inlet and smoke outlet

Underground buildings are closed, and in order to ensure the normal smoke exhaust effect, air supply outlets should generally be set up. The setting of air inlet and air outlet is an important problem.

Set points are as follows:

(1) The air supply outlet can be set in this smoke-proof partition or in other smoke-proof partitions. When the air supply outlet and the smoke exhaust outlet are arranged in the same smoke-proof partition wall, the air supply outlet should be arranged below the lower edge of the smoke storage bin, and the air supply outlet should be kept as far as possible from the smoke storage bin and the smoke exhaust outlet, so as not to disturb the smoke and avoid the mixed flow of the smoke caused by the collision of cold and hot air currents;

(2) the horizontal distance between the air supply outlet and the smoke outlet should not be

(3) The size of the smoke outlet should not be determined simply by the diameter of the connecting air duct, but by the calculation of the effective ventilation area;

(4) For the smoke outlet of the ground shaft or external wall, the size and height shall be marked according to the provisions of the building code.

2. Setting of exhaust fan room

In order to ensure that the smoke exhaust fan can run normally and continuously for 30 minutes under the smoke exhaust condition and prevent the fan from being directly threatened by flame, a safe space is needed to place the smoke exhaust fan. When conditions are limited, there should also be fire fighting.

The key points of setting the smoke exhaust fan room are: the smoke exhaust fan should be set in a special machine room, and the machine room should be separated from other parts by a partition wall with a fire resistance limit of not less than 2.0h, a 1.5h floor and a Class A fire door.

3, smoke fire damper and fire damper settings

Smoke exhaust fire damper is generally used in the pipeline of smoke exhaust system and is in a closed state. In case of fire, it needs to be opened automatically or manually to give full play to its smoke exhaust function. When the smoke temperature in the pipeline reaches 280℃, it will be automatically closed.

Fire dampers are generally placed in the air supply and return ducts of air conditioning or ventilation systems and are in an open state. When the gas temperature in the pipeline reaches 70℃, the fusible piece will melt, and the valve will automatically close under the action of torsion spring, thus playing the role of smoke exhaust.

The main points of setting smoke exhaust fire damper or fire damper are as follows:

(1) Fire dampers or smoke exhaust fire dampers should be set near the fire separation zone according to the requirements of building codes, and should not be more than 200mm away from the wall. When there are difficulties, the air duct between the above-mentioned air valves and the fire separation zone should take heat insulation and fire prevention measures;

(2) The setting of fire dampers shall be carried out according to the provisions of Building Code;

③ There is no need to repeatedly set fire dampers on the exhaust shaft and exhaust branch pipes.

4, special occasions smoke control settings

According to the building code, when the total area of underground buildings (rooms) and windowless rooms on the ground is more than 200 square meters or the area of one room is more than 50 square meters, or when there are many combustibles and people often stay, smoke exhaust facilities should be set up. However, in practical engineering, some equipment rooms in the basement did not consider the restrictions of the code, and only set up smoke exhaust facilities according to the area requirements.

The main points of smoke exhaust facilities in some parts of underground buildings are as follows:

(1) There is no parking in the water pump room, power distribution room (using dry-type transformer, low oil or vacuum switch) or generator room, and less combustible materials are used at the same time, so there is no need to set up a smoke exhaust system;

② For swimming pools, skating gymnasiums and shooting gymnasiums, there is no need to set up smoke exhaust systems;

(3) For expensive equipment rooms, archives rooms and collection room, that is, rooms with high fire possibility, gas fire extinguishing systems need to be set up. The working principle of gas fire extinguishing system is to spray fire extinguishing agent through a limited space, and then suffocate to extinguish the fire. These rooms should be equipped with automatic valve closing control system and ventilated after fire.

5, underground, ground * * * stair smoke control settings.

When there is a fire in the basement, the high-temperature toxic smoke will spread to the upper floor through the stairwell under the buoyancy, so the stairwell connecting the upper floor of the building with the basement is separated by fire doors as required, and the corresponding mechanical smoke control and exhaust system is set up according to the requirements of the code. However, in design practice, it is often easy to ignore the influencing factors of fire doors. In order to avoid the overlapping of air ducts, a set of pressurized air supply system is still used on the ground and underground, and the pressurized air supply outlet adopts electric tuyere. The author thinks this method is not very reliable, because once a fire breaks out in the underground part, fireworks will spread to the above-ground part, which will greatly hinder the evacuation of the above-ground part. Therefore, for the smoke prevention system, when a fire occurs, the pressurized air supply volume of the ground and underground parts needs to meet the requirements at the same time to avoid potential safety hazards.

Common problems of smoke control and exhaust system in underground buildings

The test results of existing smoke control and extraction systems show that most of the existing smoke control and extraction systems in underground buildings have some problems, such as insufficient smoke discharge, insufficient residual pressure of mechanical air supply system compared with the requirements of the code, the layout of tuyeres does not meet the requirements of the code, and the automatic opening and closing of valves cannot be realized.

The specific reasons are as follows:

1. At the stage of scheme design, designers have some problems, such as being unable to connect with reality, having a blunt understanding of national codes, and designing out of thin air by unilaterally referring to some clauses and tables in the codes, without taking into account the actual situation in specific projects, the construction technical level of the construction unit and other factors.

2. For the construction unit, it is difficult to construct in strict accordance with the design drawings and related atlas, and the requirements for fan selection are quite different from those for design selection. In the construction process, due to lax management, the fan box is seriously deformed, the surface roughness of the air duct does not meet the specification requirements, the net area of the air duct section does not meet the design requirements, the selection of the corresponding fire valve has not been certified by the relevant state departments, and the supervision unit is not serious and responsible, which easily leads to the failure of the smoke control and extraction system to fully play its role.

3. In operation, the operational ability and regular maintenance level of managers have not been strengthened, and it is impossible to prepare for fire at any time.