What is the vent hole of the chimney

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Exhaust ports are designed for flue and liquid fuel vents, which can not be swept directly into the chimney. The borehole must be designed above the roof of the building or in the loft space into which chimneys can be discharged. The floor of the swath must be at least 600 mm and at most 1200 mm above the floor. The distance is no more than 6 m from the chimney vents. Width should be more than 120 mm and height at least 180 mm. In the vicinity of the hole, the space must be adjusted and the access must be easy. The hole must be fitted with a closed chimney door. The living quarters must be located on the corridor, staircase, hall, chamber or bathroom and toilet. The clear height must not be less than 1.7m and the area must be illuminated.