FAQ - Frequently-asked questions

See all the answers to frequently-asked questions. It may be the quick way to find the solution to your query.

The flue, or flue gas extraction system, is the system that expels the flue gases generated by combustion to the outside. It consists of three parts: the union or flue gas duct (pipe or connecting element between the stove - or fireplace - and the flue); the chimney or flue (the vertical part); the chimney pot which constitutes the final part of the flue.

Before installing a stove or fireplace it is always necessary to check on the feasibility - compatibility of the existing plant – and the presence of any bureaucratic restrictions. The installer must therefore check on the suitability of the room where the system will be installed, on the presence of other appliances already installed (even if powered by different fuels) so as to ensure that installation is permitted. It is also a good idea to check that the position of the appliance in the installation room is conducive to basic operations such as fuel loading, maintenance and ash cleaning/removal. The suitability of the flue gas extraction system, if it already exists, is essential, as is evaluating the possible need for ducting to repair or renovate the flues. As regards the products used to construct the flue gas extraction system, they will have to have the specific designation that they are compatible with the characteristics of the stove or fireplace that will be installed. It is worth remembering that the law states that when an installer has completed the installation, he/she must issue a declaration of conformity of the system complete with the user and maintenance manual of the stove or fireplace, and a photocopy or printed photograph of the chimney flue plate and plant log book.

As regards the frequency of maintenance operations for heating systems, the UNI 10683 standard indicates that: “heating system maintenance should be performed on a regular basis and in accordance with the operating and maintenance manual of your stove or fireplace, as well as in compliance with legal requirements and/or local regulations.” As regards cleaning the smoke duct and flue, all soot must be removed in accordance with the provisions of UNI 10847

Flues must be insulated because this avoids sudden drops in flue gas temperatures and helps with their expulsion. The majority of pipes in circulation today used for flues are already adequately insulated.

With wood-burning appliances, when the draft is excessive due to an oversized flue, they operate with very high, bright flames, and combustion is fast which leads to the consumption of wood loads in a short space of time. Obviously, the best way to resolve the situation is to install a compliant flue and resize it as required by instruction manual of the stove or fireplace, but this is not always possible. Fortunately there are some remedies that can solve the majority of situations:

  • if the system is equipped with a flue gas adjustment, you can close it completely or partially in order to slow down the combustion
  • you could also intervene on the primary and secondary air adjusters to decrease the intake of combustion air into the firebox.

As specified by UNI 10683: “collective flues are not allowed nor can you connect up extraction ducts from kitchen hoods of any kind or from any other kind of discharge from other generators into the same chimney or smoke duct”.
However, you are allowed to have a system composed of a fireplace and baking oven with a single discharge point towards the chimney flue and the manufacturer must provide the constructional characteristics for the fitting of the flue gas ducts.

It is mandatory and specified in UNI 10683 that every stove or fireplace is suitably connected to a flue gas extraction system fit to ensure adequate dispersion in the atmosphere of combustion products.

Combustion products must be discharged at roof height. It is prohibited to discharge products directly through the wall or into enclosed spaces, even with access to clear sky. The components of systems used to extract combustion products must be suitable for the specific operating conditions and in compliance with the relevant product standards. Ref. UNI 10683 standard