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HE prime function of a chimney is to produce a draft that will cause
sufficient combustion and carry off the resulting smoke; incidentally
it assists ventilation. Many unsatisfactory heating plants and much
excessive fuel consumption are due to improperly constructed chimneys,
which are the rule rather than the exception. Although many of these are
more inefficient than dangerous, yet reports of the National Board of
Fire Underwriters[1] show that a larger number of fires are caused by
defective chimney construction than by anything else. The annual loss
resulting from such fires is greater than the fire loss from any other
cause. Poor chimney construction is responsible for smoke pollution of
the air, waste of fuel, and poor heating.
[1] "Dwelling Houses," a publication issued by the National Board of
Fire Underwriters in the interest of fire protection, has been used as
a basis for the matter relating to the requirements and construction of
chimneys and methods of fire protection.
The most common faults in chimney construction are:
1. The use of unsuitable materials. Clay sewer pipe, hollow building
blocks, or unprotected concrete should not be used.
2. Improper laying of brick. Brick should not be laid on edge and should
be properly bonded. Lining should be used in all brick chimneys the walls
of which are less than 8 inches thick. Lack of mortar, especially in the
perpendicular joints, ruins many an otherwise good chimney.
3. Failure to support the chimney properly. It should never be carried
on any timber construction of the building, and when it rests upon the
ground sufficient masonry foundation should be provided to prevent
settling.
4. Building inflammable material into the chimney or against it without
proper insulation.