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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
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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
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
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
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!!!
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