In our daily life, there is a door that should always be kept closed. Do you know which one it is? It's the fire door that is normally closed. However, many people often leave it open for convenience, which can lead to greater casualties in the event of a fire.
The normally closed fire door is a type of fire door that can meet the requirements of fire stability, integrity and thermal insulation within a certain period of time. It is installed in fire compartments, evacuation staircases, vertical shafts and other fire-resistant compartments.
Besides its normal purpose as a door, the fire door also has the function of blocking fire spread and smoke diffusion. It can prevent the spread of fire for a certain period of time and ensure the evacuation of personnel.
The data released by the Ministry of Public Security shows that about 60% of the victims of smoke poisoning and death were in evacuation channels, corridors, and even homes far from the fire point. This is because the flow direction of smoke is the path of fire spreading, and the speed of smoke spreading is very fast.
Fire experts pointed out that the vertical flow rate of smoke is 3-5 meters per second, which is 8-10 times the horizontal flow rate and exceeds the fire spread rate by 5 times. For example, in a 33-story building, smoke can spread from the lower floors to the top floor through the evacuation stairs in about 30 seconds without any obstacles.
The normally closed fire door is in a closed state during normal times, and needs to be pushed open when people walk through. However, there are some shortcomings in opening a normally closed fire door because the installation location of the fire door is usually a passageway where people often walk through, leading to contradictions. In particular, in large shopping malls with a large flow of people, if normally closed fire doors are installed in the evacuation staircase, they will soon be damaged and fall off due to frequent opening and closing, which will form a hidden danger.
The normally open fire door is in an open state during normal times and automatically closes in case of fire. It is kept open for easy access and ventilation and can close itself in the event of a fire to prevent smoke and fire, thereby completely solving the inconvenience caused by the normal closing of the fire door to personnel passage and the artificial damage caused by frequent opening and closing of the fire door, while ensuring fire safety. Therefore, normally open fire doors should be installed in evacuation staircases of some large shopping malls, which should be in an open state during normal times, and be closed by door closers controlled by various sensors in case of fire.
Normally open fire doors should be used in places where people frequently pass through in the building, including smoke-proof staircases, firefighting elevator lobbies, and shared lobbies. The fire doors in the hall evacuation aisle should also be normally open fire doors.
Except for the locations where normally open fire doors are allowed, normally closed fire doors should be used for all other fire doors. In other words, unless indicated as normally open fire doors on the drawing, all other fire doors should be normally closed fire doors. This requires that when selecting fire doors, the design personnel must indicate in the door and window table if the specifications require normally open fire doors, which can be reviewed by the reviewers accordingly.