Consider the smoke exhaust design of buildings

2021-07-23 852

Large scale fire cases have proved that smoke is the main cause of fire, and more than 80% of victims are killed directly or indirectly by smoke. Scientific and reasonable design of window opener control is very important to delay the spread of fire and ensure safe evacuation time. In the past few decades, smoke control (or smoke exhaust) has become the focus of international fire departments and architectural design. This paper analyzes the current situation of smoke exhaust design, points out the shortcomings of current laws and regulations, and describes some problems related to practical work in daily work.

1. Current situation of anti exhaust design

The research on mechanical anti emission technology began only in the mid-1980s. During the "85" and "95" periods, he carried out a lot of research on the stairs of high-rise buildings and underground shopping areas, and achieved some remarkable results. However, these studies mainly focus on the actual process, lack of systematic research, basic experiment and basic theoretical research. So far, there is no national standard for the architectural design and construction inspection of some smoke control systems, and the design requirements of smoke control are simply incorporated into the relevant fire protection design standards.

Two types of public buildings (excluding recreational facilities) not exceeding 32 m shall not be considered waste facilities. The limit for installing stairs to prevent smoke is 32 meters, but it is unreasonable to set standards for installing smoke exhaust facilities. According to regulations, smoke emission from passages, courtyards and rooms without windows cannot be considered in high-rise ordinary Hotels with a building height of 32 M. The same number of laminated hotels can meet the following conditions, such as secondary fire resistance, double self system installation, closed stairs, etc., but must also meet the smoke emission requirements. This is obviously unreasonable.

In order to meet the requirements of environmental assessment, many customs stores were "closed". Therefore, most entertainment places are equipped with mechanical window opening machines for smoke exhaust. In contrast, in a multi-storey building, the building area of rooms on the first, second and third floors is 200 square meters, and the total length of rooms on the fourth, fourth and above floors, underground and semi underground rooms and corridors is 20 m or more. The window opener must be installed in corridors with a length of more than 20 m, windowless rooms with a floor area of 100 m2 or more, rooms with fixed windows or underground rooms with an area of 50 or more in high-grade private buildings.

Keeping smoke within a certain range, such as partition wall, smoke curtain wall (curtain) and smoke curtain beam (wall), is the basic method to control smoke. The design and review personnel set the fire compartment as the focus of fire protection design. At present, the design of the defense department in large non large ceiling places such as underground, automobile, large warehouse and large supermarket is relatively strict. The design of the defense department in decoration engineering is ignored, and most of them are design units. There is no explanation of relevant defense zones. Generally, all defense zones are divided by channel and calculated by exhaust channel area. It is clearly specified and channels are set as required. Rooms (including semi underground and underground rooms) are not provided. The doors leading to rooms and channels are fire doors. In this case, the partition can be divided to prevent smoldering only through the channel. If doors leading to rooms and passages are not fire doors, smoke compartments shall include these rooms. When the room (including semi basement and basement) is equipped with exhaust facilities according to regulations, the channel has no exhaust facilities, and the channel and channel leading to the room are fire doors, but each room can be separated to prevent smoldering; If the door leading to the room and passage is not a fire door, please provide a passage in the smoke compartment.

When installing the mechanical smoke exhaust room, the ventilation system shall be installed, and the ventilation volume shall not exceed 50% of the smoke exhaust volume. However, the downwind location was not disclosed. The air supply outlet is installed near the ceiling to facilitate construction and management. Some researchers used smoke simulation software to compare different wind protection plans and study the shadow of mechanical smoke emission. As a result, it is found that when the auxiliary air outlet is installed above the upper part or the ground, the auxiliary wind directly impacts the smoke layer and accelerates the sinking of the smoke. The vent is designed to facilitate the bottom of the space. In addition, the wind direction and speed of mechanical supplementary wind are also important factors affecting the flue gas emission effect. Designers need to comprehensively consider and select a more reasonable scheme.



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