Consider the smoke exhaust design of buildings

Large scale fire cases have proven that smoke is the main cause of fires, with over 80% of victims directly or indirectly killed by smoke. Scientific and rational design of window opener control is crucial for delaying the spread of fire and ensuring safe evacuation time. In the past few decades, the issue of smoke prevention and exhaust has become a focus of attention for international fire departments and the field of building design. This article analyzes the current situation of smoke exhaust design, points out the shortcomings of current regulations, and describes some issues related to daily work and practical work.

1. Current situation of anti exhaust design

The research on mechanical anti emission technology only began in the mid-1980s. During the "85" and "95" periods, he conducted a lot of research on staircases in high-rise buildings and underground shopping areas, and achieved some significant results. However, these studies mainly focus on practical processes and lack systematic research, basic experiments, and fundamental theoretical studies. So far, there is no national standard for building design and construction inspection of certain smoke prevention systems, and the design requirements for smoke prevention have been simply incorporated into relevant fire protection design standards.

Two types of public buildings (excluding recreational facilities) that do not exceed 32 meters cannot be considered waste facilities. The limit for installing stairs to prevent smoke is 32 meters, but setting standards for installing smoke exhaust facilities is unreasonable. According to regulations, smoke emissions from passages, courtyards, and windowless rooms cannot be considered in high-rise ordinary hotels with a building height of 32 meters. The same number of stacked hotels can meet the following conditions, such as secondary fire resistance, dual self system installation, enclosed stairs, etc., but must also meet smoke emission requirements. This is obviously unreasonable.

In order to meet the requirements of environmental assessment, many customs shops have been "closed". Therefore, most entertainment venues are equipped with mechanical window openers for smoke exhaust. In contrast, in a multi story building, the building area of rooms on the first, second, and third floors is 200 square meters, while the total length of rooms on the fourth, fourth, and higher floors, underground and semi underground rooms, and corridors is 20 meters or more. Window openers must be installed in corridors longer than 20 meters, windowless rooms with a floor area of 100 square meters or larger, rooms with fixed windows, or underground rooms with an area of 50 square meters or larger in high-end private buildings.

Keeping smoke within a certain range, such as partition walls, smoke curtain walls (curtains), and smoke curtain beams (walls), is the basic method for controlling smoke. The design and review personnel have set fire compartments as the focus of fire protection design. At present, the design of defense departments in large non large suspended ceiling places such as underground, large automobile warehouses, and large supermarkets is relatively strict, and the design of defense departments in decoration projects is ignored, mostly by design units. There is no explanation for the relevant defense zones, usually all defense zones are divided by channels and calculated based on the exhaust channel area. Clearly stipulate and set up passages as needed, do not provide rooms (including semi underground and underground rooms), and doors leading to rooms and passages are fire doors. In this case, the separation can be divided to prevent smoldering solely through the channel. If the doors leading to the rooms and passages are not fire doors, the smoke compartment should include these rooms. When ventilation facilities are installed in rooms (including semi basement and basement) according to regulations, there are no ventilation facilities in the passages. The passages leading to the room are fire doors, but each room can be separated to prevent suffocation; If the door leading to the room and passage is not a fire door, please provide a passage in the smoke compartment.

When installing a mechanical smoke exhaust room, a ventilation system should be installed and the ventilation rate should not exceed 50% of the smoke exhaust rate. However, the location of the downwind has not been made public. The air supply outlet is installed near the ceiling for the convenience of construction and management. Some researchers compared different windbreak plans using smoke simulation software and studied the shadows of mechanical smoke emissions. As a result, it was found that when the auxiliary air outlet was installed at a position higher than the upper part or the ground, the auxiliary wind directly hit the smoke layer and accelerated the sinking of the smoke. The ventilation holes are designed to facilitate the bottom of the space. In addition, supplementing the wind direction and speed through mechanical means is also an important factor affecting the effectiveness of flue gas emissions. Designers need to consider comprehensively and choose a more reasonable solution.