\"Technical Code for Smoke Prevention and Exhaust in Buildings\" – Design of natural ventilation and mechanical ventilation

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I. Requirements for the installation of natural ventilation facilities 1. In enclosed stairwells and smoke-proof stairwells that rely on natural ventilation, an openable exterior window or opening with an area of not less than 1.0 m2 should be provided at the highest point； When the building height is greater than 10 m, operable exterior windows or openings with a total area of not less than 2.0 m2 shall also be provided on the outer wall of the stairwell every 5 floors, with an installation interval of not more than 3 floors. 2. When natural ventilation is used in the front room, the area of external windows or openings that can be opened in separate front rooms and front rooms for fire elevators should be no less than 2.0 m2, while in shared front rooms, this area should be no less than 3.0 m2. 3. Shelter floors (rooms) that utilize natural ventilation shall be equipped with operable exterior windows facing different directions; their effective area shall not be less than 2% of the floor area of such shelter floor (room), and the area for each direction shall not be less than 2.0㎡. 4. Operable exterior windows should be easy to open directly. For those located at a height where direct opening is not convenient, manual opening devices should be installed at a height of 1.3m–1.5m above the ground. II. Requirements for the installation of mechanical pressurized air supply systems 1. In buildings with a height greater than 100m, their mechanical pressurized air supply systems should be designed as separate vertical sections, with each section having a height of no more than 100m. 2. Unless otherwise specified in this standard, smoke-proof stairwells and their antechambers that utilize mechanical pressurized air supply systems shall be equipped with separate air supply shafts (ducts), air supply outlets (valves), and air supply fans. 3. For buildings with a height of 50 m or less, when it is difficult to install pressurized air supply ducts in the stairwells, a direct-air-supply pressurized ventilation system can be used for these stairwells, and the following requirements must be met: For high-rise buildings with a height greater than 32 m, air should be supplied to two points in the stairwell, with the distance between these supply points being no less than half of the building’s height ； The air supply volume shall be the calculated value or the value specified in Article 3.4.2 of this standard, increased by 20% ； Pressurized air supply outlets should not be located in areas that affect personnel evacuation. 4. For the above-ground and below-ground sections of stairwells equipped with a mechanical pressurized air supply system, such systems should be installed separately in each section. When constrained by building conditions and the underground portion serves as a garage or equipment room, a shared mechanical pressurized air supply system can be used, and the following requirements must be met: The air supply volume for the above-ground and underground portions shall be calculated separately in accordance with the provisions of this standard, and the sums of these values shall constitute the air volume for the shared pressurized air supply system ； Effective measures should be taken to meet the air supply requirements for the above-ground and below-ground sections respectively. 5. For mechanical pressurized air supply fans, axial flow fans or medium/low pressure centrifugal fans are preferred. Their installation shall comply with the following requirements: The inlet of the air supply fan shall lead directly to the outside, and measures shall be taken to prevent smoke from being drawn in ； The air inlet of the supply fan should be located at the lower part of the mechanically pressurized air supply system ； The inlet of the supply fan should not be on the same plane as the outlet of the exhaust fan. When difficulties do exist, the inlet of the supply fan and the outlet of the exhaust fan should be arranged separately; when arranged vertically, the inlet of the supply fan should be located below the exhaust outlet, with a minimum vertical distance between their edges of 6.0 m ； When arranged horizontally, the minimum horizontal distance between their edges should not be less than 20.0 m ； The supply fan should be located at the lower part of the system, and measures should be taken to ensure uniform air supply throughout all floors ； The supply fan should be installed in a dedicated machine room, and such a room must comply with the provisions of the current **standard, the Code for Fire Protection Design of Buildings GB 50016 ； When check valves or electric valves are installed on the exhaust duct or intake duct of the supply fan, measures should be taken to ensure that the valves open automatically in case of a fire. 6. The installation of pressurized air supply outlets shall comply with the following provisions: Except for the direct-pressure air supply method, an open louvered air supply outlet should be provided in stairwells every 2 to 3 floors ； Each floor of the antechamber shall be equipped with a normally closed pressurized air supply outlet, along with a manual operation device ； The wind speed at the air outlet should not exceed 7 m/s ； The air outlet should not be located in areas blocked by doors. 7. The mechanically pressurized air supply system shall use ducted air supply, and civil construction air ducts shall not be used. The air supply ducts should be made of non-combustible materials and have a smooth inner surface. When the inner wall of the air supply duct is metal, the design wind speed should not exceed 20 m/s ； When the inner wall of the air supply duct is non-metallic, the design wind speed should not exceed 15 m/s ； The thickness of the air supply ducts shall comply with the provisions of the current **standard, the ‘Code for Acceptance of Construction Quality of Ventilation and Air Conditioning Engineering’ GB 50243. 8. The installation and fire resistance rating of mechanical pressurized air supply ducts shall comply with the following provisions: Vertically installed air supply ducts shall be installed separately in duct shafts; when this is not feasible, air supply ducts that are not installed in duct shafts or share a duct shaft with other ducts shall have a fire resistance rating of not less than 1.00 hour ； For horizontally installed air supply ducts, when installed within a ceiling, their fire resistance rating shall not be less than 0.50 hours ； When not installed in a ceiling, its fire resistance rating shall not be less than 1.00 hour. 9. The duct shafts of mechanical pressurized air supply systems shall be separated from adjacent areas by partition walls with a fire resistance rating of not less than 1.00 hour; if maintenance doors must be installed on such walls, they shall be of Class B fire doors. 10. In areas where mechanical pressurized ventilation is used, louvered windows should not be installed, and operable exterior windows are also not advisable. 11. In enclosed stairwells and smoke-proof stairwells equipped with a mechanical pressurized air supply system, a fixed window of not less than 1 m2 shall also be installed at their top. For smoke-proof stairwells located against an exterior wall, fixed windows with a total area of not less than 2 m2 shall also be provided on that exterior wall every 5 floors. 12. When installing a mechanical pressurized air supply system in a refuge floor (room), operable exterior windows shall also be provided on the exterior walls, and their effective area shall not be less than 1% of the floor area of that refuge floor (room). The calculation of the effective area shall comply with the provisions of the technical standards.