hergom CRETA Instructions D'installation, De Service Et De Maintenance page 26

When wood is burned slowly, tar and other organic vapours are produced,
which when combined with the damp in the environment form tar. Tar vapours can
condense if the walls of the chimney are cold. If tar is set alight this could produce
high temperature fires. Any accumulation of tar must be eliminated.
Due to the fact that the accumulation of tar depends on so may variables it
is very difficult to foresee when the chimney has to be cleaned.
A visual inspection is the surest way to see if your stove is free from tar.
For this reason we recommend that the equipment is installed so that it can
be easily accessed.
3. - Options
If a chimney is going to be built for the Crete stove you have two
alternatives:
a) Brick chimneys.
b) Metal chimneys
Studies show that there is not a great deal of difference between the
efficiency of the draft between brick and metal chimneys. The choice is up to you.
Whenever possible build you chimney inside the house where the draft will
be better, there will be less tar and it will last longer.
The advantages of brick chimneys are:
a) The mass of bricks and small slabs reduce the cooling of smoke in
the chimney.
b) The ability of the bricks to accumulate heat allows the house to
stay hot longer after the fire has gone out.
c) It can be built to your own specifications.
d) If it is constructed correctly it could be more resistant to heat than a
metal chimney.
Brick chimneys must be lined correctly to prevent smoke from cooling.
They must be constructed with materials which support high temperatures
and corrosion.
They can be round, square etc. as what matters is the size of the chimney.
For brick chimneys a Crete stove must comply with the measurements given
in the section on TECHNICAL SPECIFICATIONS.
The advantages of metal chimneys are:
a) They are easy to install.
b) They allow slight changes in the direction of the chimney, which
gives greater flexibility in the choice of the place where the stove is to be installed.
c) There are no curved bends and angles to impede the draft.
4. – Regulations
Below please find some other regulations which must be complied with
when a chimney is built.
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