The steel fire door is made of steel material to make the door frame and the steel fire door: the frame of the door fan and the panel of the door fan, and with fire-resistant hardware components composed of a certain fire-resistant performance of the door.
    Class A fire door, fire resistance limit 1.5 hours.
    Class B fire door, fire resistance limit 1.0 hours.
    Class C fire door, fire resistance limit 0.5 hours.