The pressurization smoke control system has been commonly used as a smoke control system at the emergency stairs of high-rise buildings. However, a higher possibility of overpressure between the lobby and the accommodation or pressure drop in the lobby could lead to failure in achievement of the purpose of pressurization system, particularly when supplying the leakage and supplementary air flow through one air-supply path at a time. To improve this particular issue, the devise configurations, as well as the different ways to supply the leakage and supplementary air flow through the different flow passages have been proposed. The performance of the trial product was evaluated on the test bed, ultimately providing a safe evacuation environment if high-rise buildings fired.
With increased advancement and integration of the cities, the demand for large-scale, high-rise and complex buildings has been on the rise, and the number of buildings vulnerable to fire has also increased. In this connection, the effective measure to prevent firing is urgently needed. In particular, the importance of smoke control system has been highlighted in the recognition of smoke as the main cause disturbing the evacuation and fire fighting activities, as well as the biggest threat to human life during fire.
In case of fire in high-rise buildings, stairwell must be tenable by preventing smoke from entering into stairwell which is a primary vertical evacuation route in order to safely evacuate occupants from the building. The stairwell pressurization method is one of the key smoke control methods, which is currently equipped in the stairwell of high-rise buildings. This method brings air from outside into stairwell through a dedicated fan to increase the pressure of stairwell, ultimately preventing smoke from entering the stairwell [
The stairwell pressurization method began to develop in earnest since 1980s and its key design guidelines were proposed in 1990s. Clark and Buckley [
Recent studies consider the ways to improve the performance by conducting a real-scale experiment and a numerical analysis on the stairwell pressurization system. Wang and Gao [
Based on these results, various countries propose the design criteria for smoke control system of emergency stairs in high-rise buildings using the stairwell pressurization system, as shown in
In Korea, “fire safety standards of smoke control facilities in the special emergency stairs” of NFSC501A is proposed as one of the fire safety standards designed to ensure the smoke safety of high-rise buildings and to prevent the penetration of the smoke from entering the smoke-control zone. In line with this, the pressurization method of smoke control to increase the pressure inside the lobby between the accommodation and the stair using a smoke control blower and an air-supply damper shown in
As described above, the key design criteria of the stairwell pressurization smoke control system for high-rise buildings being used in key countries including Korea were established in around 1980s to 1990s, and these were involved in the fire safety standards of each country. The countries have realized the importance of the stairwell pressurization smoke control system that protects stairwell from smoke; however, the recent relevant studies and reports have confirmed the failure of the existing stairwell pressurization smoke control system in
Nation | Fire safety standards (smoke control system part) |
---|---|
The U.S. | NFPA 92A |
IBC (1022.9, 909.20) | |
Europe | EN 12101-6 |
China | GB 50045 (8.3) |
Korea | NFSC 501A |
satisfying the criteria on safe evacuation set by each country. This implies the ineffectiveness of pressurization smoke control system currently installed at stairwell in offering a safe evacuation environment during fire [
In this study, a field evaluation was conducted on 2 high-rise buildings equipped with the pressurization smoke control system in order to evaluate the performance of the pressurization smoke control system of stairwell being installed and operated at the high-rise buildings. The results drawn from the field performance evaluation were analyzed; and as a result, a separate air-supply method has been proposed as a way to improve the existing pressurization smoke control system of stairwell. This new method is known to supply the air for leakage and supplementary through the different flowing paths. The design methodology of the separate air-supply method of pressurization smoke control, as well as the result of performance evaluation conducted in test bed have been proposed.
In this study, a field evaluation was conducted on 2 high-rise buildings equipped with the pressurization smoke control system in order to evaluate the performance of the pressurization smoke control system of stairwell being installed and operated at the high-rise buildings. The indoor pressure in the accommodation, lobby and stairs during the operation of the smoke control systems has been measured and examined.
As shown in
systems.
As identified in the figures, the pressure difference between the accommodation and the lobby was 97 Pa on the 2nd floor after operating the pressurization smoke control system, whereas the pressure difference between the accommodation and the lobby at the 11th and 18th floors was recorded in the range of 112 Pa and 124 Pa, showing much higher value compared to the design value, 50 Pa. As mentioned above, the higher pressure difference generated between the accommodation and the lobby is much likely to be difficulty for evacuees to open the evacuation exit.
As shown in
As identified in the figures, the pressure difference between the accommodation and the lobby was 48 Pa on the 3rd floor with all doors kept closed, while decreasing down to approximately 23 Pa with the door at a lobby left opened. The pressure difference at the 30th floor was decreased from about 82 Pa to 46 Pa. As clarified above, the pressure of lobby and stairs at each floor may decline if the door at the lobby is kept opened.
As identified above, the issues associated with the existing pressurization smoke control systems are the pressure drop or overpressure between the accommodation and the lobby upon the opened or closed condition of the door. As to improve this issue, the devise configurations, as well as the different ways to supply the leakage and supplementary air flow through the different flow passages have been proposed as follows.
In the separate air-supply type of pressurization smoke control system, the leakage air flow and the supplementary air flow are supplied separately to the lobby of each floor through the different flow passages. That is, the leakage air flow is supplied to the lobby on each floor through the leakage air flow supplying blower, the leakage air flow duct and the leakage air flow blade of damper. The supplementary air flow is supplied to the lobby on each floor through the supplementary air flow supplying blower, the supplementary air flow duct and the supplementary air flow blade of damper, as shown in
Status of the door of lobby | Status of air supply to lobby | Effect |
---|---|---|
Closed | Only leakage air flow is supplied | · Maintaining the proper pressure difference · Preventing overpressure between the lobby and the accommodation |
Opened | Only supplementary air flow is supplied | · Forming a critical air velocity · Preventing the leakage air from out flowing through the opened door |
To operate the pressurization smoke control system of separate air-supply type effectively, the air supply damper needs to be developed as a key component to provide and control the leakage and supplementary air flow depending on the pressure formation conditions. In this connection, the intelligent air supply damper of double- blade type was developed in this study. As shown in
In this study, the separate air-supply type of pressurization smoke control system was installed at 5-story experiment building to conduct the real-scale performance evaluation. A floor plan of the experiment building being used as the test bed in this study is shown in
Air supply blower and control panel were installed in the equipment room on the rooftop. The pressure differential between the lobby and the accommodation of each floor, and opening ratio of the blades for the leakage air flow and the supplementary air flow were saved on the control panel in a real-time manner.
As mentioned above, the pressure differential (ΔP2) between the lobby and the accommodation was set at 50
Status of the door of lobby | Status of pressure differential (ΔP) between the accommodation and the lobby | Operating condition of leakage air flow blade | Operating condition of supplementary air flow blade |
---|---|---|---|
Closed | ΔP is higher than ΔP1 | · Opened in case ΔP is higher than ΔP1 · PID-controlled to maintain ΔP to be ΔP2 | Closed in case ΔP is higher than ΔP1 |
Opened | ΔP is lower than ΔP1 | · Closed in case ΔP is lower than ΔP1 | Completely opened in case ΔP is lower than ΔP1 |
Pa, the target of the blade for controlling the leakage air flow in the performance evaluation, whereas the pressure differential (ΔP1) between the lobby and the accommodation was set at 10 Pa, the opening condition of blade for controlling the supplementary air flow.
The experiment was conducted while activating a separate air-supply type of pressurization smoke control system from 60 seconds after the experiment began. The emergency doors of the lobby on the 5th, 4th, and 3rd floors are kept opened and closed in order, from 180 seconds after the operation started. From this experiment, it is able to identify the results of pressure differential status and the operation performance of double-blade air supply damper on each floor under following two different conditions: 1) all of emergency doors on 3 floors are closed; 2) emergency doors on some floors are opened.
The results of performance evaluation conducted at the test bed are shown in
Upper graph in the figure shows the pressure difference between the lobby and the accommodation, while middle graph and bottom graph show opening ratio of leakage air flow blade and supplementary air flow blade in the air supply damper, respectively. From the experiment, it was found that if pressure difference between the lobby and the accommodation is under 50 Pa, the leakage air flow blade in the air supply damper is opened more widely and the flow rate of leakage air which is supplied to the lobby increases. If the flow rate of leakage air increases and pressure difference between the lobby and the accommodation goes up over ΔP2 later, opening ratio of leakage air flow blade is changed, resulting in adjusting the flow rate of leakage air and pressure difference between the lobby and the accommodation to be matched to the designed pressure differential (ΔP2). If the door of the lobby is opened and the pressure of the lobby falls down to around “0”, the supplementary air flow blade is opened fully to supply enough supplementary air flow to form critical air velocity to the accommodation; at the same time, the leakage air flow blade in the air supply damper is completely closed to prevent leakage air flow from outflowing. The graphs from the experiment of each floor show the results from simultaneous experiments. Based on the graphs, it is confirmed that although the door of certain lobby is opened, it does not have any effect on other lobby, and each lobby is operated independently.
From the results of experiment, it is expected that the separate air-supply type of pressurization smoke control system will solves the issues associated with the overpressure between the compartments, including the pressure down with the lobby door opened. This system is also highly expected to effectively ensure the performance of smoke control system for a safe evacuation.
The importance of smoke control system has been highlighted in the recognition of smoke as the main cause disturbing the evacuation and fire fighting activities, as well as the biggest threat to human life during fire. In line with this, the pressurization smoke control system has been commonly used in Korea to prevent the penetration of the smoke from entering the emergency stairs.
The field evaluation on the operating performance of the pressurization smoke control system was carried out, targeting the multiple high-rise buildings currently in operation. However, a higher possibility of overpressure between the lobby and the accommodation or pressure drop in the lobby could lead to failure in achievement of the purpose of pressurization system, particularly when supplying the leakage and supplementary air flow through one air-supply path at a time.
In connection with the improvement of this problem, a key concepts of the separate air-supply type of pressurization smoke control system was introduced which separated the leakage air flow and supplementary air flow through different flow passages, and the operating principles and structure of the double-blade air supply damper were also suggested that was a key component for providing separate air supply effectively.
The trial product of a separate air-supplied pressurization system developed through the studies was installed at the 5-story test bed to conduct the performance test; and as a result, it is expected that the separate air-supply type of pressurization smoke control system will solve the issues associated with the overpressure between the compartments, including the pressure down with the lobby door opened. This system is also highly expected to effectively ensure the performance of smoke control system for a safe evacuation.
This study was conducted based on the relevant study, “Technology Development of Large Space Structures Have More than 3-Hour Fire-Resistance Rating and Smoke-Control/Evacuation in Fire”, a major project conducted by Korea Institute of Civil Engineering and Building Technology.