Chimney Fires
Chimney Fires
Construction, Challenges
Fire Control Best Practices
Objectives
• Review different types of chimney
construction
• Identifying lines vs. unlined flues
• Understand fire spread characteristics of
most common chimney types
• Effective fire control practices
Chimney Construction
• The chimney method
of smoke removal has
been around for
centuries
• Early man discovered
the benefits of vertical
draft methods in
removing smoke from
caves, huts, etc.
Chimney Construction (cont.)
• Various means to
construct vertical
drafts (chimneys)
used:
–
–
–
–
–
Stone
Mud/sticks
Hollow logs
Bricks
Metal (modern)
Attachment Methods
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•
•
•
•
Interlock wall stones with chimney stone
Free-standing
Wall logs interlocked in stone or brick
Metal ties to wall framing (20th century)
Metal bracing within wood framework
(modern zero-clearance chimney piping)
Lined Flue
• Inside of chimney
construction contains
flue “pipe” or “lining”
that minimizes
openings, joints, or
crevices along vertical
path of heat, smoke,
embers
Metal Chimney Liner
Tile Chimney Liner
Liner Characteristics…
• Each type of liner has it’s benefits and
drawbacks…
– Metal is expensive, but crack resistant and often
installed in one piece top-to-bottom.
– Most common sizes are 6- and 8- inch
– Easy connection to wood/coal stoves
– Can be routed through some twists and turns
– Can retrofit old, unlined flues
Liner Characteristics (cont.)
• Tile, or terra cotta, offer wider passages
than metal and are less expensive than metal
• Not used in retrofits or relining of existing
flues
• Susceptible to temperature extremes and
settling of foundations, causing cracking
• May consist of several joints
Zero-Clearance or Prefabricated
Metal Chimney Flues
• Developed nearly 25
years ago to service
the growing
alternative heating
market
• Consist of multiple
layers of stainless steel
separated by fireretardant insulation
Unlined Flues
• Found in many homes
built prior to 1930
• May be of stone or
brick construction
Unlined Flues (cont.)
Fire Spread Characteristics
Tile/Terra Cotta Liners
• Cracks appearing over time and temperature
extremes provide openings for hot
ash/embers to exit the flue and contact
adjacent combustible framing members
• May also provide path into void spaces,
carrying sparks into area containing
combustibles (attic, behind knee wall)
Terra Cotta/Tile Liner (cont.)
• Subject to degradation
from rain, ice, snow
• Mechanical damage
from improper
cleaning, previous
fires
• Damage introduced
from exterior forces
(wind, trees)
Metal Chimney Liners
• May warp from
extremes in
temperature (burning
stove too hot)
• Improper attachment
of flue sections
Metal Flues (cont.)
• Joints may be open, allowing sparks and
embers to escape into void and combustible
spaces adjacent to chimney, permitting fire
spread and slow detection of same.
• Stainless steel tubular liners are used in
older unlined retrofitting, often resulting in
turns and twists permitting build up of
creosote and animal nests.
Creosote Buildup
• Creosote is a
byproduct of
INCOMPLETE
combustion.
• Adheres to tile,
unlined, flexible
metal, and joints in
flue liners
Creosote (cont.)
• Relatively cool temperatures in upper
portion of flue condense products of
combustion into potential “time bombs” on
liners.
• Can be minimized by burning proper fuels
(seasoned wood) at proper temperature
recommended by stove/fireplace
manufacturer
Animal Nest in Chimney Flue
Retrofitting Unlined Flues
• It is common to find older, unlined
chimneys outfitted with new style flexible,
stainless steel tubular liners
• Often connect to wood stove or insert
• May be placed in unlined flue surrounded
by fire-resistant material such as a
vermiculite/gypsum mix
Prefabricated Metal Chimneys
• Have Class “A” fire rating and may be used
inside of wooden box framing according to
building codes and Underwriter’s
Laboratories test results
• Lock together in a twisting motion
• Are NOT fire PROOF!!!
Identifying Fire Presence and
Control Options
Caller Complaints
• Hear persistent “roaring” sound from upper
flue area
• Smoke from chimney when no active fire in
fireplace/ stove
• Haze/smoke odor in upper floors of house
and/or attic
• Walls adjacent to chimney hot to touch
Fire Control Tactics
• Thermal Imager A MUST!!!!
• Get personnel ABOVE and BELOW
fireplace/stove-check walls, floor space
adjacent to flue--attic
• Check flue clean out (if present)
• Roof crew to check openings at top
Tactics (cont.)
• Remove active fire from firebox
• Closely monitor flue for active flames
• Consider use of dry chemical extinguisher
or “chimney bombs” (dry chem in plastic
baggies dropped from top of chimney)
• Pressurized water extinguisher and/or
preconnect should be LAST RESORT
• Once fire controlled, occupant must be
directed to have licensed chimney sweep
clean and inspect chimney PRIOR to ANY
additional usage.
• Officer should document this on NFIRS
report.
Points to Consider…
• Successful control of chimney fires requires
time and patience
• Continual monitoring of all adjacent
combustible areas required during
operations
• Older, unlined flues often contain structural
framing members tying chimney to house
Other Important
Considerations…
• EARLY laddering of roof
• Use of chimney chains to clear flaming
creosote (if available on scene)
• Aggressive investigation of adjacent void
spaces
• Identification of lined vs. unlined flue
Summary
• Firefighters should be familiar with the
various chimney types
• Understand particular hazards of each
type of flue
• Recognize signs of active fire situations in
flue and execute proper control methods
Summary (cont.)
• Make every attempt to control fire while
minimizing damage to chimney/flue
structure
• Ensure safe operations when working in
poor lighting and on wet/icy or steep roof
pitches
• Have a safe, happy, injury- and fire-safe
holiday season!!!!!