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

•  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 fire-retardant 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