National standards specify clear requirements for the gap dimensions at the overlapping points of fire doors: for steel fire doors, the overlap between the door leaf and the frame must be at least 10 mm, while the gaps on either side between the leaf and the frame must not exceed 4 mm. Excessive gaps after installation compromise the door's airtightness, thereby undermining its ability to contain fire and smoke during an actual blaze.
Therefore, the width of the installation gaps must be strictly controlled. Adhering to these standards ensures the fire door functions effectively; consumers should personally supervise the installation process to prevent issues such as substandard workmanship or the use of inferior materials, thereby ensuring the door does not fail to protect lives in the event of a fire.
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