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KEEPING YOUR CHIMNEYS AND FLUES OPERATING
PROPERLY
Chimneys Are Made to Protect You
A chimney is a structure made of masonry or metal,
which surrounds and supports a flue or multiple flues
that vent products of combustion from gas, oil, or solid
fuel appliances or fireplaces. The flue, then, is the
inner part of the chimney, the part that actually
contains and vents the products of combustion. Flues
can be made of clay, as in the case of most masonry
chimneys, or of metal, as in the case of prefabricated
or manufactured chimneys.
One way to think of a chimney and flue within it is to
think of it as a structure built to protect you. That is an
important function of all chimneys no matter what kind
of appliance or fireplace they serve.
Remember, the main purpose of a chimney is to vent
the products of combustion from your home. That
function is crucial because the products of combustion
contain hazardous and noxious gasses. One of the
hazardous gasses your chimney needs to remove from
your home is carbon monoxide.
Carbon monoxide is a colorless, odorless, tasteless
gas that can cause serious illness or death when it is
present in sufficient amounts. It is responsible for
hundreds of deaths and countless illnesses every year
in homes across America. In many cases carbon
monoxide in the home originates in a furnace or other
burning appliance and finds its way into the house due
to inadequate venting.
What causes inadequate venting? There are several
possibilities. One is that the flue has become blocked.
The blockage can come from debris falling into the
chimney due to a deteriorating masonry chimney, or, it
may be the result of nests built there by animals or
birds. Carbon monoxide can also seep into the house
through cracks or holes in flues and chimneys that
moisture, chemical residue, or chimney fires have
damaged.
The other important function of chimneys, especially
those serving solid fuel burning appliances like wood
stoves or fireplaces, is to keep excessive heat from
combustible materials that surround the chimney. Heat
or flames from a chimney fire can escape through
cracks in the clay flue liner or through damaged or
missing mortar joints of a chimney. They can then
ignite surrounding combustible framing members of a
house.
Chimney fires occur within the structure of the
chimney itself. They happen when hot flue gasses or
cinders ignite creosote accumulated on the walls of an
unclean chimney flue. Creosote is a natural byproduct
of burning wood. It is highly flammable and will
accumulate on the inner walls of the flue under certain
burning conditions.
Even without the occurrence of a chimney fire, framing
members surrounding a chimney can have their
molecular structure altered and become more
flammable when exposed to excessive heat over long
periods of time. This process is known as pyrolasis.
Once wood is sufficiently pyrolized it can ignite at
relatively low temperatures and becomes a significant
fire hazard.
So, you see, a well structured chimney and flue are
designed to offer protection to your family and home
from both the dangers of noxious gasses such as
Carbon Monoxide, and from the high levels of heat
present in the flue gasses of solid fuel burning
appliances and fireplaces. But, like all structures, they
must receive regular inspections and maintenance in
order to maintain their integrity and to continue doing
their job. More Info......
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