Chimney Fires

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Chimney Fires
Chimney Fires

• Construction, Challenges
• Fire Control Best Practices

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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

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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.

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Chimney Construction (cont.)

• Various means to construct vertical drafts
  (chimneys) used
• Stone
• Mud/sticks
• Hollow logs
• Bricks
• Metal (modern)

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Attachment Methods

• 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)

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Lined Flue

• Inside of chimney construction contains flue
  pipe or lining that minimizes openings,
  joints, or crevices along vertical path of heat,
  smoke, embers

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Metal Chimney Liner
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Tile Chimney Liner
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Liner Characteristics

• Each type of liner has its 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

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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

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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 fire-retardant insulation

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Unlined Flues

• Found in many homes built prior to 1930
• May be of stone or brick construction

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Unlined Flues (cont.)
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Fire Spread Characteristics
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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)

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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)

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Metal Chimney Liners

• May warp from extremes in temperature (burning
  stove too hot)
• Improper attachment of flue sections

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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.

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Creosote Buildup

• Creosote is a byproduct of INCOMPLETE combustion.
  
• Adheres to tile, unlined, flexible metal, and
  joints in flue liners

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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

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Animal Nest in Chimney Flue
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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

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Prefabricated Metal Chimneys

• Have Class A fire rating and may be used inside
  of wooden box framing according to building codes
  and Underwriters Laboratories test results
• Lock together in a twisting motion
• Are NOT fire PROOF!!!

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Identifying Fire Presence and Control Options
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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

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Fire Control Tactics

• Thermal Imager A MUST!!!!
• Get personnel ABOVE and BELOW fireplace/stove-chec
  k walls, floor space adjacent to flue--attic
• Check flue clean out (if present)
• Roof crew to check openings at top

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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

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• 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.

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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

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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

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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

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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

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• Have a safe, happy, injury- and fire-safe holiday
  season!!!!!