Insufficient positive pressure supply air in the smoke-proof stairwell; during a fire, smoke enters the evacuation stairwell and threatens escape safety.
The smoke control and exhaust system is the core system for ensuring safe evacuation during a building fire. Statistical data show that approximately 85% of fire deaths are caused by smoke inhalation. GB 51251-2017 "Technical Standard for Smoke Control and Exhaust Systems of Buildings" is the most core standard reference. Based on the requirements of GB 51251-2017 and GB 15930-2007, this article systematically analyzes the design, construction and maintenance key points of smoke control and exhaust systems.
The pressurization air supply of the smoke control system is installed in smoke-proof stairwells, vestibules, refuge floors and fire elevator vestibules, forming positive pressure through mechanical air supply to prevent smoke intrusion. The pressure difference between the stairwell and the corridor is 40 to 50 Pa, and the pressure difference between the vestibule and the corridor is 25 to 30 Pa. The stairwell is provided with normally open louver air outlets at alternate floors, and the vestibule is provided with normally closed electric air outlets at each floor. The air supply volume is calculated according to the standard for simultaneously opening the vestibule air outlets of 2 to 3 floors.
The smoke exhaust system is divided into two types: natural smoke exhaust and mechanical smoke exhaust. Natural smoke exhaust adopts openable exterior windows or top skylights, and the effective area of smoke exhaust windows shall not be less than 2% of the floor area. Mechanical smoke exhaust is provided with smoke exhaust fans and smoke exhaust outlets, and the horizontal distance from the smoke exhaust outlet to the farthest point shall not be greater than 30 m. The area of a smoke control zone should not exceed 500 square meters. The makeup air volume shall not be less than 50% of the smoke exhaust volume. Smoke exhaust ducts shall be made of non-combustible materials.
Fire dampers close at 70°C and are used where ventilation and air-conditioning systems penetrate fire compartments. Smoke fire dampers close at 280°C and are installed at the inlet of smoke exhaust fans and on smoke exhaust ducts penetrating fire compartments. The actuation temperatures of the two are different: fire dampers close at 70°C, while smoke fire dampers need to withstand a high temperature of 280°C and remain open in the early stage of a fire to facilitate smoke exhaust. Valve actuation signals should be fed back to the fire control room.
The steel plate thickness for duct fabrication shall be selected according to the standard: 0.75 mm or more for medium- and low-pressure systems and 1.0 mm or more for high-pressure systems. Ducts are connected by flanges or common flanges, and the sealing gaskets shall be non-combustible materials. Reinforcement is required when the side length is greater than 630 mm. Smoke exhaust outlets shall be no less than 1.0 m from combustibles. Flexible connections between fans and ducts shall be provided, and vibration isolators shall be installed on the foundation. Check monthly whether the manual opening of air outlets is flexible. Test the remote start of fans and the electric opening of air outlets quarterly. Conduct air volume testing every six months.
The importance of smoke control and exhaust systems in hotel operations cannot be ignored. Hotel guest room corridors are long, people are dense, and most are travelers unfamiliar with evacuation routes; a reliable smoke control and exhaust system is the lifeline for ensuring safe evacuation. The daily maintenance focus of the pressurization air supply system includes checking whether air supply outlets are obscured or blocked by decoration, whether fan belts are loose, and whether ducts leak air. The key test of the smoke exhaust system lies in whether the smoke exhaust outlets of each smoke control zone can open normally after a fire signal is triggered and interlock with the start of the smoke exhaust fan. The hotel engineering department should conduct a comprehensive smoke control and exhaust system test every six months, including pressure difference measurement of stairwells and vestibules, air volume testing of smoke exhaust fans, and emergency power switching tests. Test data shall be recorded and filed for reference, and any failure to meet pressure difference and air volume requirements shall be rectified immediately.
The design, construction and acceptance of smoke control and exhaust systems involve coordinated cooperation among multiple disciplines. In the design stage, hydraulic calculations and airflow organization simulation of the smoke control and exhaust system should be carried out to ensure that system performance meets the standard requirements. In the construction stage, the fabrication and installation quality of ducts should be strictly controlled, and duct air leakage testing should be carried out during installation. Fire dampers should be installed where ducts penetrate fire walls and floor slabs, and the installation positions of valves should facilitate inspection and maintenance. The arrangement of smoke exhaust outlets should avoid airflow short-circuiting, and the distance between smoke exhaust outlets and air supply outlets should preferably not be less than 20 m. The acceptance of smoke control and exhaust systems should include two stages: single-unit testing and interlock testing. Single-unit testing includes fan operation testing, air outlet opening testing and valve actuation testing. Interlock testing should simulate a fire signal and check the interlock sequence and time of the system from detector alarm to air outlet opening and fan start. The power supply of smoke control and exhaust systems should adopt fire power supply, with dual-circuit supply and automatic switching at the end. Fan control boxes should be provided with manual control buttons and remote control functions from the fire control room. Through comprehensive design, construction and acceptance management, ensure that the smoke control and exhaust system can operate reliably during a fire.
The design, construction and acceptance of smoke control and exhaust systems involve coordinated cooperation among multiple disciplines. In the design stage, hydraulic calculations and airflow organization simulation of the smoke control and exhaust system should be carried out to ensure that system performance meets the standard requirements. In the construction stage, the fabrication and installation quality of ducts should be strictly controlled, and duct air leakage testing should be carried out during installation. Fire dampers should be installed where ducts penetrate fire walls and floor slabs, and the installation positions of valves should facilitate inspection and maintenance. The arrangement of smoke exhaust outlets should avoid airflow short-circuiting, and the distance between smoke exhaust outlets and air supply outlets should preferably not be less than 20 m. The acceptance of smoke control and exhaust systems should include two stages: single-unit testing and interlock testing. Single-unit testing includes fan operation testing, air outlet opening testing and valve actuation testing. Interlock testing should simulate a fire signal and check the interlock sequence and time of the system from detector alarm to air outlet opening and fan start. The power supply of smoke control and exhaust systems should adopt fire power supply, with dual-circuit supply and automatic switching at the end. Fan control boxes should be provided with manual control buttons and remote control functions from the fire control room. Through comprehensive design, construction and acceptance management, ensure that the smoke control and exhaust system can operate reliably during a fire. The daily inspection of smoke control and exhaust systems should include fan operation status inspection, duct integrity inspection, air outlet patency inspection and fire damper status inspection. Fan belts should be checked quarterly for tension and wear, and belts that are loose or severely worn should be replaced promptly. Duct connecting flanges should be regularly checked for loose bolts and aged sealing gaskets. Air outlet louvers should be kept clean and unblocked, and manual actuators should operate flexibly. The temperature control release devices of fire dampers should be checked every six months, and those exceeding their validity period should be replaced promptly. The annual testing of smoke control and exhaust systems should be entrusted to a qualified fire detection agency, and the testing content includes fan flow and pressure testing, duct air leakage testing, air volume distribution testing of air outlets on each floor, and system interlock function testing. Any failure in testing shall be immediately arranged for repair and rectification to ensure that the system is always in good condition.
The daily inspection of smoke control and exhaust systems should include fan operation status inspection, duct integrity inspection, air outlet patency inspection and fire damper status inspection. Fan belts should be checked quarterly for tension and wear, and belts that are loose or severely worn should be replaced promptly. Duct connecting flanges should be regularly checked for loose bolts and aged sealing gaskets. Air outlet louvers should be kept clean and unblocked, and manual actuators should operate flexibly. The temperature control release devices of fire dampers should be checked every six months, and those exceeding their validity period should be replaced promptly. The annual testing of smoke control and exhaust systems should be entrusted to a qualified fire detection agency, and the testing content includes fan flow and pressure testing, duct air leakage testing, air volume distribution testing of air outlets on each floor, and system interlock function testing. Any failure in testing shall be immediately arranged for repair and rectification. Duct cleaning of smoke control and exhaust systems is also an important part of maintenance management. Long-term operation inside ducts will accumulate dust and oil contamination, affecting air volume and possibly becoming an ignition source. The duct cleaning cycle should be determined according to the use environment: kitchen smoke exhaust ducts should be cleaned quarterly, and ordinary air-conditioning ducts should be cleaned annually. The installation of smoke control and exhaust systems in special areas of hotels also has specific requirements. The smoke exhaust system of hotel kitchens should be provided separately and not shared with the air-conditioning system. The exhaust system of hotel laundry rooms should be provided with fire dampers. The smoke exhaust system of hotel entertainment venues should meet the fire protection standard requirements for song and dance entertainment venues. The smoke exhaust system of hotel banquet halls and large conference rooms should interlock with the fire alarm system. Through comprehensive maintenance management, ensure that the smoke control and exhaust system can operate reliably during a fire.
Duct cleaning of smoke control and exhaust systems is also an important part of maintenance management. Over prolonged operation, dust and oil accumulate inside ducts, reducing airflow and potentially becoming an ignition source. The duct cleaning cycle should be determined according to the operating environment: kitchen exhaust ducts should be cleaned quarterly, and ordinary air-conditioning ducts annually. The smoke control and exhaust system also has specific requirements for installation in special areas of hotels. The exhaust system of a hotel kitchen should be installed separately and not shared with the air-conditioning system. The exhaust system of a hotel laundry should be provided with a fire damper that closes automatically when the exhaust temperature exceeds 70°C. The smoke exhaust system of hotel entertainment venues should meet the fire protection code requirements for song-and-dance entertainment venues. The annual inspection of the smoke control and exhaust system should be entrusted to a qualified fire inspection agency, covering fan flow and pressure tests, duct air leakage tests, airflow distribution tests at outlets on each floor, and system linkage function tests. Any inspection failure should be immediately followed by repair and rectification to ensure the system remains in sound condition at all times. The smoke control and exhaust system is the core system for ensuring safe evacuation of occupants in a building fire; its reliable operation is directly related to life safety and must be given high priority.
The fan bearings of the smoke control and exhaust system should be lubricated once a year, and the lubricating oil should be selected according to the manufacturer's recommendations. The vibration isolation foundation of the fan should be inspected once a year to ensure good vibration isolation performance. The electrical control system of the smoke control and exhaust system should be inspected regularly, including whether the wiring in the control box is loose, whether the contactor contacts are worn, and whether the thermal relay is functioning properly. Duct air leakage testing should be carried out during installation. Fire dampers should be installed where ducts penetrate firewalls and floor slabs, and the damper installation position should be accessible for inspection and maintenance. The arrangement of smoke exhaust outlets should avoid airflow short-circuiting, and the distance between smoke exhaust outlets and supply air outlets should preferably not be less than 20 m. The importance of the smoke control and exhaust system requires that we give it high priority, ensuring through comprehensive maintenance management that it performs its due function in a fire and safeguards safe evacuation of occupants.
Through all-round design, construction, and acceptance management and standardized maintenance and testing, ensure that the smoke control and exhaust system always remains in a sensitive and reliable working state, providing a solid guarantee for building fire safety.