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9.7. The chimney flue
In addition to the general requirements applicable to the smoke duct and to the chimney flue, the chimney flue:
Must only be used to discharge smoke.
Must be correctly sized to meet smoke evacuation requirements (EN 13384-1 non-exhaustive example)
Is preferably insulated, made of steel and with a circular inner cross-section. If rectangular, the edges must
normally have a radius of not less than 20 mm and a ratio between internal dimensions <1.5.
Normally have a minimum height of 1.5 metres.
Maintain a constant cross-section.
Be waterproof and thermally insulated to ensure draught.
Preferably have a collection chamber for unburnt material and any condensation.
If pre-existing, it must be cleaned, to avoid fire hazards.
As a general guideline, it is advisable to duct the chimney flue if its diameter is greater than 150 mm, the
assessment of which is the responsibility of the technician in charge of sizing the system.
9.8. Ducted system
In addition to the general requirements applicable to the smoke duct and to the chimney flue, the ducted system:
Must operate under negative pressure.
Must be inspectable.
Must comply with local regulations.
9.9. The chimney pot
Must be windproof.
Must have an inner cross-section equivalent to that of the chimney flue and an outlet smoke passage cross-
section equal to at least twice the inner cross-section of the chimney flue.
In the case of paired chimney flues (which should be at least 2 m apart), the chimney pot that receives the solid
fuel product discharge or that of the highest floor must be at least 50 cm above the other.
Must go beyond the reflux area (in Italy, refer to Standard UNI 10683)
Must allow for maintenance operations to be performed on the chimney
9.10. External air intake
In general, we suggest two alternative ways of ensuring the flow of essential air for combustion:
indirect air intake
direct air intake
9.11. Indirect air intake
Prepare, at floor level, an air intake with a useful surface area (net of any meshes or other protections) of at least 80
cm2 (diameter 10 cm).
In order to avoid draughts, it is advisable to place the air intake behind the stove or behind a radiator.
It is advisable not to have it in front of the product to avoid draughts.
9.12. Direct air intake
Prepare an air intake with a useful cross-section (net of any meshes or other protection) with a surface area at least
equal to the cross-section of the air inlet hole behind the product.
Assess the diameter according to the pressure drops.
Connect the air intake to the hole with a pipe, even a flexible hose.
Increase the diameter of the pipe if the pipe is not smooth: assess the pressure drops.
It is advisable not to exceed 5 m and to have no more than 3 bends, depending on the chimney flue draught.
