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

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