By Gene Padgitt, CFI, and Marge Padgitt
Many house fires occur due to flammable bird or squirrel nests in or around
chimneys. On Monday, February 10, 2014, Gene found a nest that was built on top
of a direct vent gas fireplace vent on the exterior of the house. The nest and wood house siding was charred,
which means that the nest was trapping heat in an area that needed to be clear
of obstructions. Heat chemically changes the structure of wood over time and
lowers the ignition point. Where wood normally ignites at approximately 500
degrees, wood exposed to heat over time may ignite at only 180 degrees or
lower. In this case, the homeowners were lucky to have had service done to
their appliance when they did or it would have gone unnoticed and eventually
caused the house to catch fire.
Shortly after the above inspection, Gene inspected another direct vent gas
fireplace and found another bird nest packed tightly inside the holes in the
vent. The homeowners had no idea that birds could get behind the vent cover and
build a fire hazard inside the vent. It is a good thing they decided to have us
do an annual gas appliance check and tune-up or it wouldn’t have been found.
 |
Flammable bird nest material
in a Direct Vent gas fireplace
vent. Homeowners should check
the exterior vent before using
each season. |
Birds and squirrels love to build
nests inside and on chimneys where they have some protection from the elements,
and heat to keep warm in the winter. Unfortunately, nests are built with
flammable dry twigs and other materials that can easily catch fire and cause a
chimney or vent fire that may become a house fire.
In 2013 we did a fire investigation
involving an unlisted decorative shroud on top of a wood chimney chase serving
a manufactured fireplace. The shroud contained over five-gallon buckets full of
squirrel nesting materials that were packed down inside the shroud and not
visible from the ground. The materials trapped heat inside the area, which in
turn ignited the combustible framing. According to the International
Residential Code, only shrouds listed for the particular manufactured appliance
may be installed. Unfortunately, there
are many architects and builders who design unlisted shrouds to cover ugly
chimney termination caps which do not have a listing and are potential fire
hazards. As chimney sweeps we need to be
diligent about checking for listed and labeled shrouds and removing those that
are not listed.
We had an unbelievable case about 18
years ago which involved the removal of over 20’ of squirrel nesting material
inside a clay tile flue liner. It took two men two trips to get all of the
material out with many types of equipment. They were almost to the point of
tearing the chimney down when they finally broke through the packed materials.
The squirrels apparently used the same location year after year and built a new
nest on top of the old nest until reaching the top.
Luckily, the homeowners had not used the fireplace for many years and
called us to inspect it before using it.
In yet another fire investigation
case in 2012, Gene found the cause of a fire to be bird nesting material packed
inside an older model manufactured chimney pipe that was designed without
adequate protection against birds. Birds
built the nest between the inner and outer pipe sections and on top of the
chase top. This blocked the air-cooled
chimney and caused it to overheat, ignited nesting materials, which in turn
ignited nearby combustibles several inches away. This is something to look for in older model
pre-fabricated fireplaces, and unfortunately, there are many of these types of
fireplaces still in use.
In 2013 we did an inspection of a manufactured
fireplace unit that had bird feathers and nesting materials coming down the
flue and through a gap at the bottom of the pipe. Further inspection revealed that nesting
materials were packed between the inner and outer chimney walls. We advised the
homeowner, who only wanted a screen installed to keep the birds out, that the
entire system was a fire hazard and needed to be replaced. This started a huge
controversy and she left negative feedback on Angie’s List. I’m sure it’s just a matter of time before
the house burns down. The sad part about this case is that another chimney
company did install a screen on the chimney cover for her and did nothing
else. What we say when this happens is
“They just bought that chimney,” which means to fire investigators that the
last person to touch it is the first person the insurance companies go after.
Chimney swifts are especially drawn
to dark, cool masonry chimneys and build their nests with mud and twigs on the
sidewalls of flues and smoke chambers. In the U.S., the Chimney Swift is
protected by the Migratory Bird Treaty Act of 1918. Neither birds nor nests can
be removed from chimneys without a federally-issued permit. Other birds build
nests on the smoke shelf or damper. All nests are flammable and are a fire
hazard. Unfortunately, the Migratory Bird Act prevents homeowners or chimney
sweeps from removing nesting birds of any type inside chimneys, and substantial
fines may apply per occurrence.
Homeowners can prevent the entry of
birds into masonry chimneys by installing a masonry chimney cover with a bird
guard screen on top of the flue or a multi-flue cap. A chimney cover serves
dual duty by also keeping rain which deteriorates mortar joints out of the flue.
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Gene and Marge Padgitt own HearthMasters, Inc. chimney and fireplace restoration company in Kansas City, Missouri.
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