Article 3.1.6 of GB 51251-2017: Closed stairwells should adopt natural ventilation systems. For closed stairwells that cannot meet natural ventilation conditions, mechanical pressurized air supply systems should be installed. When the enclosed stairwells of underground or semi underground buildings (rooms) are not shared with the above ground stairwells and the underground is only one floor, mechanical pressurized air supply systems may not be installed. However, the first floor should be equipped with openable external windows with an effective area of not less than 1.2m2 or evacuation doors that directly lead to the outside..
Article 3.2.1 of GB 51251-2017: For enclosed stairwells and smoke proof stairwells using natural ventilation, an openable external window or opening with an area of no less than 1.0m2 should be installed at the highest point; When the building height is greater than 10m, openable external windows or openings with a total area of no less than 2.0m2 should be installed every 5 floors on the exterior walls of the stairwell, and the spacing should not exceed 3 floors..
Article 1.0.9 of Part 2 of the “Guidelines for the Application of Non mandatory Provisions in Fire Protection Design of Building Projects in Shandong Province” states that for enclosed stairwells or smoke proof stairwells on the ground, underground, or second floor with a height difference of less than or equal to 10m between the indoor floor and the outdoor entrance floor, natural ventilation can be used, but ventilation conditions must be met, that is, a total area of no less than 2.0m should be set up every 5 floors ² Can open external windows or openings, and the top has an area of no less than 1.0 m ² Can open external windows or openings. (Among them, 2.0m) ² The openable external window or opening may include an area of no less than 1.0 m set at the highest point ² (Can open external windows or openings).
Article 4.2.2, Paragraph 1 of the Technical Guidelines for Fire Protection Design Review and Acceptance of Construction Projects in Shandong Province (HVAC): For enclosed stairwells with underground floors less than or equal to 2 and a height difference of less than or equal to 10 meters between the indoor floor and the outdoor entrance floor, the total area of open external windows or openings on the first floor above ground should not be less than 2.0 meters ²， The window area at the highest part of the staircase should not be less than 1.0m ² Natural ventilation and smoke prevention methods can be used..
In summary, for enclosed stairwells or smoke proof stairwells on the underground second floor with a height difference of less than or equal to 10m between the indoor floor on the ground floor and the outdoor entrance floor, the total area of open external windows or openings on the first floor above ground shall not be less than 2.0m ²， The window area at the highest part shall not be less than 1.0m ² Natural ventilation and smoke prevention methods can be used..
