1. Mechanical Pressurized Air Supply System and Its Components Setup1. System Setup Requirements(1) For buildings with a height greater than 100m, the mechanical pressurized air supply system in the smoke-proof stairwell and its foyer should be vertically segmented and independently set, and the service height of each segment should not exceed 100m.(2) Unless otherwise specified, the smoke-proof stairwell and its foyer using the mechanical pressurized air supply system should have independent air supply shafts (ducts), air supply outlets (valves), and air supply fans.(3) For buildings with a height less than or equal to 50m, if it is difficult to set up pressurized air supply shafts (ducts) in the stairwell, a direct injection pressurized air supply system may be used. For high-rise buildings greater than 32m, the air supply should be done from two points in the stairwell, with the distance between air supply outlets not less than 1/2 of the building height. Pressurized air supply outlets should not be set in locations that affect personnel evacuation.(4) When both the basement and semi-basement stairwells need to be equipped with a mechanical pressurized air supply system, they should be independently set. When building conditions limit this and the underground part is a car park or equipment room, the underground part can share the mechanical pressurized air supply system with the above-ground stairwell, but the pressurized air supply volume for above-ground and underground should be calculated separately and then combined as the shared pressurized air supply system volume, with effective measures taken to meet the air supply requirements for both above-ground and underground.(5) The mechanical pressurized air supply system in the refuge floor (room) should also have openable external windows on the outer wall, with an effective area not less than 1% of the floor area of the refuge floor (room).(6) For stairwells with mechanical pressurized air supply systems that are adjacent to outer walls or directly lead to the roof, smoke-proof stairwells should have normally closed emergency smoke exhaust windows installed at the top or on the outer wall of the highest floor, and these emergency smoke exhaust windows should have manual and interlocking opening functions.2. Mechanical Pressurized Air Supply FanThe mechanical pressurized air supply fan can be an axial flow fan or a medium/low-pressure centrifugal fan, and its installation position should meet the following requirements:(1) The inlet of the air supply fan should preferably directly connect to the outdoor and measures should be taken to prevent smoke from being sucked in.(2) The inlet of the air supply fan should be located at the lower part of the mechanical pressurized air supply system.(3) The inlet of the air supply fan should not be located on the same side as the outlet of the smoke exhaust fan. When it must be located on the same side, the inlet of the air supply fan and the outlet of the smoke exhaust fan should be arranged separately, and when arranged vertically, the inlet of the air supply fan should be set below the outlet of the smoke exhaust fan, with a minimum vertical distance of not less than 6m; when arranged horizontally, the minimum horizontal distance should not be less than 20m.(4) The air supply fan should be located in a dedicated machine room.(5) When installing one-way dampers or electric dampers on the air supply or inlet ducts, measures should be taken to ensure that the dampers automatically open during a fire.3. Pressurized Air Supply OutletsPressurized air supply outlets are required to be set up in two forms: normally open and normally closed as follows:(1) Except for direct injection air supply methods, stairwells should have one normally open louvered air supply outlet set every 2-3 floors.(2) The foyer should have one normally closed pressurized air supply outlet set on each floor, and should have a manual opening device.(3) The wind speed of the air supply outlet should not exceed 7m/s.(4) The air supply outlet should not be located in positions blocked by doors.It should be noted that places using mechanical pressurized air supply should not have louvers and should not have openable external windows.4. Air Supply Ducts(1) Air supply shafts (ducts) should be made of non-combustible materials, and the inner surface of the ducts should be smooth, with the duct’s sealing performance meeting fire conditions for pressurized air supply.(2) Vertically set air supply ducts should be independently set in duct shafts. When this is difficult, air supply ducts that are not set in duct shafts or share duct shafts with other ducts should have a fire resistance limit of not less than 1.00h.(3) Horizontally set air supply ducts, when set in ceiling spaces, should have a fire resistance limit of not less than 0.50h. When not set in ceiling spaces, the fire resistance limit should be not less than 1.00h.(4) When using metal ducts, the duct wind speed should not exceed 20m/s; when using non-metal material ducts, it should not exceed 15m/s.5. Pressure Relief ValveThe pressure relief valve is a valve that controls the pressure difference. To ensure the positive pressure value in the smoke-proof stairwell and its foyer, fire elevator foyer, and shared foyer, and to prevent the positive pressure from being too high, making evacuation doors difficult to push open, pressure relief valves should be set between the smoke-proof stairwell and the foyer, and between the foyer and the corridor, controlling the pressure difference across the pressure relief valve should not exceed the design value.2. Design Calculation Requirements for Mechanical Pressurized Air Supply System1. Calculation of Pressurized Air Supply VolumeThe mechanical pressurized air supply volume for enclosed refuge floors (rooms) and refuge corridors should be calculated based on the net area of the refuge floor (room) and refuge corridor at no less than 30m³/h per square meter. The air supply volume for the foyer of the refuge corridor should be calculated based on the total cross-sectional area of the evacuation door leading directly to the foyer multiplied by the wind speed of 1.0m/s.2. Selection of Pressurized Air Supply VolumeThe design wind volume of the mechanical pressurized air supply system should fully consider duct losses and leakage, and should not be less than 1.2 times the calculated wind volume.3. Relevant Regulations on Wind PressureThe mechanical pressurized air supply volume should meet the pressure distribution from the corridor to the foyer to the stairwell, and the pressure relief value should meet the following requirements:(1) The pressure difference between the foyer, shared foyer, enclosed refuge floor (room), enclosed stairwell, and evacuation corridor should be 25-30Pa.(2) The pressure difference between the smoke-proof stairwell and the evacuation corridor should be 40-50Pa.(3) When the system’s pressure relief value exceeds the maximum allowable pressure difference, pressure relief measures should be taken.3. Setting of Natural Smoke Exhaust Systems and Their Components(1) Smoke exhaust windows should be set at the top or outer wall of the smoke exhaust area and should meet the following requirements:1) When set on the outer wall, the smoke exhaust window should be within the smoke storage chamber, but the natural smoke exhaust windows in areas where the corridor and indoor space net height is not greater than 3m can be set at a position above 1/2 of the indoor net height. Based on the characteristics of smoke rising flow, the higher the position of the smoke exhaust outlet inside the building, the better the smoke exhaust effect, therefore, smoke exhaust outlets are usually set near the top of the wall or on the ceiling. When the room net height is less than 3m, the lower edge of the smoke exhaust outlet should be above 1/2 of the total height of the room.2) The opening form should facilitate the discharge of smoke. When the room area does not exceed 200㎡, the opening direction can be unrestricted.3) It is advisable to distribute evenly, and the length of each group of smoke exhaust windows should not exceed 3m.4) The horizontal distance between smoke exhaust windows set on both sides of the fire wall should not be less than 2m.5) The horizontal distance from any point in the indoor or corridor to the nearest smoke exhaust window in the smoke-proof area should not exceed 30m; when the public building space net height is greater than or equal to 6m and has conditions for natural convection, the horizontal distance should not exceed 37.5m. When industrial buildings use natural smoke exhaust, the horizontal distance should not exceed 2.8 times the net height of the space within the building.6) A manual opening device that is easy to operate should be set near the automatic smoke exhaust window, with a height from the ground of 1.3-1.5m.(2) When setting up natural smoke exhaust systems for atriums with a net height greater than 9m, and for multi-functional halls, exhibition halls, etc., with a building area greater than 2000㎡, a central manual opening device and automatic opening facilities should also be set.(3) The effective area of the natural smoke exhaust window (opening) can be opened in the form of side-opening windows and top-opening windows. Side-opening windows include upper-hung windows, middle-hung windows, lower-hung windows, casement windows, and side-pull windows, etc. In the design, these must be set as windows used for smoke exhaust in the smoke storage chamber. If the lower opening part of the middle-hung window is not within the smoke storage chamber, this part’s area cannot be counted as effective smoke exhaust area. When calculating the effective smoke exhaust area, the side-pull window is calculated based on the actual opened area, and other forms of windows are calculated based on their opening projection area.1) When the opening angle of the window is greater than 70°, it can be considered as basically fully opened, and the effective smoke exhaust area can be considered equal to the window area. When the opening angle is not greater than 70°, for hung windows, it should be calculated based on the horizontal projection area; for casement windows, it should be calculated based on the vertical projection area.2) When using louvered windows, it should be calculated based on the effective opening area of the window.(4) The external window setting for factories and warehouses should meet the following requirements:1) Side windows should be evenly set along both opposing sides of the building.2) Top windows should be evenly set on the roof and should preferably be opened using automatic control; for roofs with a slope less than or equal to 12°, a corresponding top window should be set for every 200㎡ of building area; for roofs with a slope greater than 12°, a corresponding top window should be set for every 400㎡ of building area.(5) Except for clean rooms, for any layer of industrial buildings such as shoe manufacturing, garment manufacturing, toys, plastics, wood processing storage, etc., where the building area exceeds 2500㎡ and natural smoke exhaust or mechanical smoke exhaust systems are set, it is advisable or permissible to set fusible skylights (windows) on the roof, and their area should comply with the following provisions:1) For buildings not equipped with automatic sprinkler systems or using steel structure roofs or prestressed concrete roof panels, it should not be less than 10% of the floor area.2) Other buildings should not be less than 5% of the floor area.3) The effective area of fusible skylights (windows) should be calculated based on their actual area.4. Setting of Mechanical Smoke Exhaust Systems and Their Components1. System Setup Requirements(1) When the mechanical smoke exhaust system of the building is arranged horizontally, the mechanical smoke exhaust system of each fire compartment should be independently set.(2) For public buildings and industrial buildings with a height greater than 50m, and residential buildings with a height greater than 100m, their mechanical smoke exhaust systems should be vertically segmented and independently set, with the service height of each segment being less than or equal to 50m for public buildings and industrial buildings, and less than or equal to 100m for residential buildings.(3) The smoke exhaust system should be set separately from the ventilation and air conditioning systems. When it is indeed difficult to separate, they can be shared, but they must meet the requirements of the smoke exhaust system, and when the smoke exhaust outlet is opened, no more than 10 control valves of the ventilation and air conditioning system should be interlocked and closed.2. Smoke Exhaust FanThe fan is the core component of the smoke exhaust system, and the smoke exhaust fan discharges high-temperature smoke. In addition to having the performance of general fans, it also needs to have high-temperature resistance. Smoke exhaust fans used in general buildings should meet the requirement of continuous operation at 280℃ for 30min. For smoke exhaust fans used in tunnels, it is required to be able to operate normally for not less than 60min at 250℃.(1) Smoke exhaust fans can be centrifugal or axial flow smoke exhaust fans (meeting the requirement of continuous operation at 280℃ for 30min).(2) Smoke exhaust fans should preferably be set at the top of the smoke exhaust system, with the smoke outlet facing upwards, and should be higher than the inlets of the pressurized air supply fan and make-up air fan. When arranged vertically, the inlet of the air supply fan should be set below the outlet of the smoke exhaust fan, with a minimum vertical distance of not less than 6m; when arranged horizontally, the minimum horizontal distance should not be less than 20m.(3) Smoke exhaust fans should be set in a dedicated machine room. There should be a space of more than 600mm on both sides of the fan. For systems that share smoke exhaust systems and ventilation air conditioning systems, the shared machine room for smoke exhaust fans and exhaust fans should meet the following requirements:1) The machine room should have an automatic sprinkler system.2) The machine room should not have fans and ducts used for mechanical pressurized air supply.3) The connecting components between the smoke exhaust fan and the smoke exhaust duct should be able to maintain structural integrity at 280℃ for not less than 30min.3. Smoke Exhaust Fire Dampers(1) Smoke exhaust fire dampers are installed on the ducts of the mechanical smoke exhaust system and are normally open. In the event of a fire, they close when the smoke temperature in the smoke exhaust duct reaches 280℃, and they should meet smoke leakage and fire integrity requirements within a certain time, acting to prevent smoke and fire. Smoke exhaust fire dampers generally consist of a valve body, blades, actuators, and temperature sensors.(2) Smoke exhaust fire dampers should have the function to automatically close at 280℃ and interlock to close the corresponding smoke exhaust fan and make-up air fan. Smoke exhaust fire dampers should be set at the following locations: on the horizontal duct segment connecting the vertical main smoke exhaust duct with each floor’s horizontal smoke exhaust duct; on the smoke exhaust branch ducts serving multiple fire compartments; at the inlet of the smoke exhaust fan; and at the points where the smoke exhaust duct crosses fire compartments.4. Smoke Exhaust Valve (Opening)The smoke exhaust valve is installed at the end of each branch of the mechanical smoke exhaust system (smoke intake opening), and is normally closed, meeting the leakage requirements. During a fire or when smoke exhaust is needed, it can be manually or electrically opened to act as a smoke exhaust valve. A valve with a decorative opening or treated with decoration is called a smoke exhaust outlet. Smoke exhaust valves generally consist of a valve body, blades, actuators, and other components.(1) The setting of smoke exhaust valves (openings) should comply with the following requirements:1) Smoke exhaust outlets should be set within the smoke storage chamber formed by the smoke-proof compartment. When dividing smoke-proof compartments with fire walls or smoke barriers, each smoke-proof compartment should have smoke exhaust outlets set separately, and the setting of smoke exhaust outlets should be determined by calculations, with the horizontal distance from any point within the smoke-proof compartment to the nearest smoke exhaust outlet not exceeding 30m.2) In places where the net height of corridors or indoor spaces does not exceed 3m, smoke exhaust outlets should be set above 1/2 of their net height, and when set on side walls, the nearest edge should not be more than 0.5m from the ceiling.(2) For rooms that require mechanical smoke exhaust systems, if the building area is less than 50㎡, smoke exhaust can be achieved through corridors, and smoke exhaust outlets can be set in evacuation corridors.(3) During a fire, the smoke exhaust valves in the smoke exhaust area should be opened in linkage with the fire automatic alarm system, and a manual opening device should be set on-site.(4) The setting of smoke exhaust outlets should ideally make the smoke flow direction opposite to the personnel evacuation direction, and the horizontal distance between the smoke exhaust outlet and the nearest safety exit should not be less than 1.5m.(5) The smoke exhaust volume of each smoke exhaust outlet should not exceed the maximum allowable smoke exhaust volume.(6) When smoke exhaust outlets are set in the ceiling and smoke exhaust is conducted through the upper space of the ceiling, the following provisions should be met:1) The ceiling should use non-combustible materials, and there should be no combustible materials within the ceiling.2) The smoke velocity at the neck of the smoke flow entry set on a closed ceiling should not exceed 1.5m/s.3) The opening rate of non-closed ceilings should not be less than 25% of the net area of the ceiling, and the openings should be evenly distributed.(7) The wind speed of the smoke exhaust outlets should not exceed 10m/s.5. Smoke Exhaust Ducts(1) Mechanical smoke exhaust ducts should be made of non-combustible materials, and the inner surface of the ducts should be smooth, with the sealing performance of the ducts meeting the requirements for smoke exhaust during a fire. When using metal ducts, the design wind speed should not exceed 20m/s; when using non-metal material ducts, the design wind speed should not exceed 15m/s.(2) The fire resistance limit of the ducts:1) Vertically set smoke exhaust ducts should be placed in independent duct shafts, and the fire resistance limit of smoke exhaust ducts should not be less than 0.50h.2) Horizontally set smoke exhaust ducts should be placed within ceiling spaces, and their fire resistance limit should not be less than 0.50h; when this is difficult, they can be set directly indoors, but the fire resistance limit should not be less than 1.00h.3) Smoke exhaust ducts set in the ceiling of corridors and those crossing fire compartments should have a fire resistance limit of not less than 1.00h, but the fire resistance limit for smoke exhaust ducts in equipment rooms and car parks can be no less than 0.50h.(3) When there are combustible materials within the ceiling, the smoke exhaust ducts should be insulated with non-combustible materials and should maintain a distance of not less than 150mm from combustible materials.5. Smoke Exhaust System Design Calculations(1) The design wind volume of the smoke exhaust system should not be less than 1.2 times the calculated wind volume of that system.(2) Except for atriums, the smoke exhaust volume calculation for the following places in a smoke-proof compartment should comply with the following provisions:1) For places with a building space net height of less than or equal to 6m, the smoke exhaust volume should be calculated at no less than 60m³/(h·m), and the value should not be less than 15000m³/h, or set effective areas of natural smoke exhaust windows (openings) not less than 2% of the room’s floor area.2) When public buildings only need to set smoke exhaust in corridors or hallways, their mechanical smoke exhaust volume should not be less than 13000m³/h, or set natural smoke exhaust windows (openings) with an area not less than 2㎡ at both ends (sides) of the corridor, and the distance between the two natural smoke exhaust windows (openings) should not be less than 2/3 of the corridor length.3) When smoke exhaust is required in both the room and corridor or hallway of public buildings, the mechanical smoke exhaust volume for the corridor or hallway can be calculated at 60m³/(h·㎡) and should not be less than 13000m³/h, or set effective areas of natural smoke exhaust windows (openings) not less than 2% of the corridor or hallway’s floor area.1) When the system serves places with the same net height, for places with a building space net height greater than 6m, the smoke exhaust volume should be calculated based on the maximum smoke exhaust volume of a single fire-proof compartment; for places with a building space net height of 6m or below, it should be calculated based on the maximum value of the sum of the smoke exhaust volumes of any two adjacent fire-proof compartments within the same fire-proof compartment.2) When the system serves places with different net heights, the smoke exhaust volume required for each place in the system should be calculated using the above methods, and the maximum value among them should be taken as the system’s smoke exhaust volume.6. Make-up Air SystemExcept for corridors of above-ground buildings or rooms with a building area less than 500m², places with smoke exhaust systems should be able to directly introduce outdoor air for make-up air, and the make-up air volume and wind speed of make-up air outlets should meet the requirements for effective smoke exhaust of the smoke exhaust system.(1) The make-up air system can use natural intake methods such as evacuation external doors, manually or automatically openable external windows, as well as mechanical air supply methods. Fire doors and windows must not be used as make-up air facilities. Fans should be set in dedicated machine rooms.(2) The make-up air system should directly introduce outdoor air, and the make-up air volume should not be less than 50% of the smoke exhaust volume.(3) The wind speed of mechanical make-up air outlets should not exceed 10m/s, and the wind speed of make-up air outlets in densely populated areas should not exceed 5m/s; the wind speed of natural make-up air outlets should not exceed 3m/s.(4) When make-up air outlets are located in the same space as smoke exhaust outlets in adjacent smoke-proof compartments, the position of make-up air outlets is unrestricted; when make-up air outlets are set within the same smoke-proof compartment as smoke exhaust outlets, the make-up air outlets should be set below the smoke storage chamber, and the horizontal distance between make-up air outlets and smoke exhaust outlets should not be less than 5m.(5) The setting of make-up air fans should meet the same requirements as mechanical pressurized air supply fans. The make-up air system required for the smoke exhaust area should be interlocked with the smoke exhaust system.
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