Fire doors are classified into wooden and steel types. Finished products must meet the fire-resistance performance requirements specified in the design and must be manufactured by production units holding a manufacturing license approved by the relevant authorities. All metal components shall be fabricated by arc welding, with welds required to be free of defects such as incomplete fusion, porosity, cracks, and burn-through. After the steel frame has been straightened, it shall comply with the applicable code requirements. Finished products must be accompanied by a factory certificate of conformity and shall be verified against the drawings to ensure compliance with the design specifications.

　　Fire doors shall be installed flush with the wall on the side where the door leaf opens.

　　The installation of wooden fire-rated door frames and leaves is the same as that of wooden door frames and leaves.

　　The fire door shall be approximately 20 mm smaller than the dimensions of the installation opening, and the door frame shall be securely fastened to the wall. Any gaps shall be tightly filled with heat-resistant materials. During installation, care must be taken to ensure straightness and to avoid sawing or planing; if such operations are unavoidable, the cut surfaces must be coated with one coat of fire-retardant paint. After chiseling or cutting out openings for hardware fittings, the exposed edges must also be coated with one coat of fire-retardant paint. Fire doors shall be attached to the wall using expansion bolts; if wooden plugs are used, they must be treated for fire resistance. In addition, a door closer must be installed on the fire door.

　　When installing the fire-rated door leaf into the rebate of the reinforced concrete door frame, first adjust the gaps around the perimeter of the leaf and frame to ensure the leaf remains perfectly aligned and plumb. The upper and lower door hinges must be aligned on the same vertical axis; when welding them securely to the embedded steel plates in the frame, verify their correct positioning to prevent displacement or deformation. The installation positions of the upper and lower latches, the bolt lock, and the handle must be precise; after a trial assembly, they should then be permanently welded in place. Upon completion of installation, conduct multiple opening-and-closing tests; only after passing inspection should the door frame be plastered and the hardware components be coated with fire-retardant paint.

　　Fire Door Closer Installation

　　Fire doors are typically installed at emergency exit passages; among them, there is a type of normally closed, fire-rated swing door that, according to fire safety regulations, must be equipped with a door closer.

　　Function of a door closer: As the name suggests, a door closer is used to close doors. In the event of a fire, when someone pushes the door open to escape, the fire door will automatically close.

　　Installation method for door closers:

　　The most commonly used door closers are surface-mounted types, and they can be installed in the following ways:

　　1. The most common standard installation method is to mount the door closer on the hinge side, on the side where the door opens. When installed in this manner, the door closer’s arm extends outward at approximately a 90° angle relative to the door frame.

　　2. The second installation method involves mounting the door closer on the side of the door opposite the hinge side, on the closing side. Typically, an additional bracket supplied with the door closer is installed on an arm that runs parallel to the door frame. This method is commonly used for exterior doors that open outward and are located on the exterior of a building, where it is undesirable to mount the door closer on the outside.

　　Install the door closer body upside down on the door frame rather than on the door itself, positioning the closer on the side opposite the door hinge. This installation method is also suitable for exterior doors that open outward, particularly when the door has only a very narrow head clearance and insufficient space to accommodate the full length of the door closer body.

　　Working principle of the door closer:

　　1. Is an automatic door-stop function required after the door is opened?

　　2. Damping and Buffering Function—Upon rapid door opening to a predetermined position, damping and buffering are activated, with the magnitude and range of the damping force adjustable according to operational requirements. This function prevents the door or lock from striking the wall when the door is forced open at high speed, and also helps prevent occupants from losing balance and leaning forward or falling during emergency evacuations caused by rapid door opening.

　　3. Delayed Slow-Closing Door—The door begins to close at a constant, slow speed from its fully open position and the closing speed can be continuously adjusted as required. This feature is particularly suitable for high-traffic areas with frequent pedestrian flow, especially in hospitals, where doors and passageways are used by elderly individuals, children, and persons with disabilities.

　　4. Adjustable closing force—This product can be installed on a wide variety of doors with significant differences in weight and width, as well as in environments where door-closing resistance is high due to external factors. The continuously variable adjustment allows for precise control of the closing force, making it particularly suitable for coastal cities and settings such as vehicles and vessels, where wind exposure causes frequent fluctuations in closing resistance (and thus the load on the door).

　　5. Operating environment: compliance with fire safety requirements and freeze-protection requirements for operation in environments where temperatures drop as low as −35°C in winter.

　　Typically, the selection of a door closer is based on the manufacturer’s product specifications, with options for different force ratings or adjustable force settings to match the size and weight of the door.

　　Additional Note:

　　In addition to installing a door closer on fire doors, double-leaf fire doors must also be fitted with a sequence controller—also referred to as a door sequencing device. The purpose of both is to ensure that the two door leaves close in a specific sequential order, thereby preventing the door from remaining partially open or ajar.

　　III. How to Resolve Issues That Arise During Fire Door Installation

　　(1) Issues in the Installation of Fire Doors

　　1. The door does not open in the required evacuation direction; it fails to open toward the evacuation route.

　　2. The fire-resistance rating of the fire doors does not meet the requirements; instead of installing Class A fire doors as specified in the design, Class B or Class C fire doors were installed.

　　3. Insufficient or absent door closers: Fire doors installed at passageways and stairwell entrances must be equipped with door closers; without them, the doors cannot meet the requirement for being normally closed.

　　4. Minimize the installation of hardware accessories. Depending on the size of the fire door, larger doors should be fitted with three hinges; however, some are installed with only two, and others with just one. For single-leaf doors that have four screw holes, only two screws are often used, thereby reducing the fastening strength.

　　5. The central joint is large, with communication on both sides and inadequate separation, making it easy for smoke to pass through and thus failing to provide effective fire-stopping separation.

　　6. The gap between the door and the floor is excessively large; according to regulations, the gap for interior doors should be maintained within the 6–8 mm range, whereas some fire-rated doors have gaps as wide as 30–40 mm.

　　7. The door gap is specified as 1.5–2.5 mm, but in some cases it can be as wide as 5 mm.

　　8. Steel door frames shall be filled with cement mortar or rock wool; however, some installations fail to do so, leaving the interior hollow.

　　9. Fire doors shall not be of the swing-door type; however, some parties deliberately convert them to swing doors, and some even fabricate swing doors using fire-resistant glass, which violates the regulations and fails to provide effective fire separation.

　　10. Openings on the sides or above fire doors have not been sealed.

　　In view of the numerous problems that arise during the installation of fire doors, in order to ensure that installed fire doors perform their intended function, the following key aspects must be rigorously addressed:

　　1. Fire compartments shall be determined in accordance with the building category and its intended use.

　　Fire-resistance zoning requirements vary among industrial buildings and warehouses, civil buildings, and underground structures, and shall be determined in accordance with the actual intended use of each building. For example, in Class I high-rise civil buildings, the area of a single fire compartment is 1,000 m²; in Class II buildings, it is 1,500 m²; in underground structures, it is 500 m²; for ordinary buildings of Classes I and II, it is 2,500 m²; and for industrial buildings, the compartment area is determined based on the production category and the classification of stored materials—such provisions are stipulated in the Code for Fire Protection Design of Buildings. Consequently, certain buildings are required to be equipped with fire doors.

　　2. Determine the type of fire door based on the requirements of the premises.

　　Based on fire-resistance rating, products are classified into three grades: Class A, Class B, and Class C. Class A has a fire-resistance duration of 1.5 hours, Class B 1 hour, and Class C 0.5 hour.

　　Based on the materials used, fire doors can be classified into steel fire doors, wood fire doors, and steel–wood composite fire doors.

　　Based on the door leaf configuration, fire doors can be classified into hinged fire doors (wooden panel doors), flush-panel fire-rated glass doors, decorative doors, and glass-and-wood doors.

　　According to installation type: single-leaf swing fire door, double-leaf swing fire door (with a staggered joint and a sealing strip in the center joint), side-sliding fire door, and electrically operated fire door.

　　3. Select fire doors appropriately in accordance with their functional requirements.

　　Fire doors are extensively used on firewalls within fire compartments and in standalone service rooms; for example, the fire control center, pump room, generator room, and electrical distribution room all employ Class A fire doors.

　　Class B fire doors shall be installed in stairwells, anterooms, and other such areas.

　　Class C fire doors shall be used in pipe shafts and cable shafts.

　　4. Install the fire door correctly in accordance with the technical requirements.

　　Door frames and door leaves may be installed either by the manufacturer or by the construction contractor, with the manufacturer providing on-site guidance and alignment. The door, door frame, and assembly must be plumb, level, and square.

　　During the installation of door frames and door leaves, attention must be paid to the door’s opening direction, which must always open in the evacuation direction.

　　The installation of steel door frames and wooden door frames may be carried out in accordance with the relevant drawings, and embedded parts can be fabricated in advance.

　　The installation gap dimensions for wooden fire doors and steel doors shall comply with the relevant regulations.

　　In summary, fire doors, together with their frames, can meet the requirements for structural stability, integrity, and thermal insulation over a specified period. In addition to performing the functions of ordinary doors, they also serve the critical purpose of preventing the spread of fire and smoke. Therefore, proper installation of fire doors ensures that, in the event of a building fire, the blaze can be effectively contained within a defined area, thereby minimizing fire-related losses and creating favorable conditions for evacuation and firefighting operations.