What door is installed in the stairwell?

The enclosed stairwell is the most important safety evacuation facility for high-rise buildings, underground buildings and large buildings. Closed stairwells refer to stairwells separated by fire-resistant building components, which can prevent smoke and hot air from entering. For stairwells with first-class fire resistance, the flammability and fire resistance limit of building components are 3.00 hours, and for stairwells with second-class fire resistance, the building components are 2.50 hours. The doors of closed stairwells should be two-way spring doors, and the doors of closed stairwells of high-rise civil buildings and high-rise industrial buildings should be Class B fire doors that open in the evacuation direction.