© 2009 Delmar, Cengage Learning

Patterns: Burn and Smoke

Chapter 11

© 2009 Delmar, Cengage Learning

Objectives

• Describe normal fire growth, direction, and the patterns fires create on building components

• Describe the impact of suppression activities on fire growth and direction and how suppression can affect the resulting burn patterns Describe unique patterns associated with concrete, glass, and steel springs

• Describe various burn pattern indicators that point to where the fire originated

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Case Study

• A store owner claimed he saw three young men throw something into the store, and he immediately saw flames

• The fire consisted of the burning of a fuel, later identified as gasoline, and little else had a chance to reach ignition temperature

• The ignitable liquid pour pattern on the floor implicated the owner himself since he was the only one with access

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Introduction

• Burn and smoke patterns are nothing more than the indicators left behind after the fire has been extinguished

• By examining these patterns, the investigator can interpret:– Direction of fire travel– Sudden growth of the fire – Eventually, the area where the fire originated

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Patterns

Figure 11-1 Patternson furnishings mayinclude sooting,heat changes, andoxidation.

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Basic Fire Patterns

Figure 11-3 A conepattern from thefire intersects andleaves marks on thewall and contents.

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Basic Fire Patterns (cont’d.)

Figure 11-4 Acircular patterndirectly over thearea of origin.What was initiallya sooted areawas then burnedclean as the firecontinued to burnand grow.

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Ceilings

• Patterns on the ceiling are a result of the fact that heat rises– Ceiling area may or may not be intact

• Sometimes the patterns are limited to an oval pattern on the ceiling when the area of origin is directly below that pattern

• Investigator needs to observe the patterns on the ceiling and compare them to the patterns on the walls

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Wall Surfaces

• DrywallFigure 11-6Sheetrock withthe paper burnedaway, leaving thegypsum exposedto the fire and firegases. Comparingthese walls toadjacent walls mayhelp determine thedirection of firetravel.

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Wood Walls

Figure 11-7 Missingsections of furringstrips on concretewalls require closeexamination; theymay not have beenburned away somuch as shorterpieces were used inconstruction.

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Wall PaperFigure 11-8Wallpaper witha plastic film onthe surface willburn differentlyfrom other typesof paper surfaces.The baseboardhas been removed,revealing a pourpattern where anignitable liquid randown the wall andcollected behind thebaseboard.

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Concrete Walls

• Must ensure that you are dealing with true concrete

• Concrete and stucco on walls will pop off as the result of heat (spalling)

• Some concrete walls are sealed with a finish to limit moisture absorption or for decoration– Sealer in some cases can become a fuel

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Doors

Figure 11-9 Door was open at the time of the fire and the V pattern is evident on thesurface of the door. The edge of the door and doorjamb where the hinges are located are alsocharred, indicating that the door was open at the time of the fire.

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Windows and Glass

• Patterns on windows close to the area of origin often are heavily damaged because of the availability of air

• Glass will fail relatively quickly in a fire • Glass shards need to be examined closely

– If they are sooted, it may indicate an explosion caused by a fire

– If they are not sooted, it may indicate that the explosion came first and caused the fire

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Windows and Glass (cont’d.)

• Crazing is when multiple small cracks that do not go all the way through the glass appear – Same effect occurs when pots are pulled from a kiln

and sprayed with a mist of water – Crazing of glass in a structural fire is most likely the

result of rapid cooling

• Burn patterns on windows also give some clues as to the fire’s development– Whether window was open or closed

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Wood Framing

• May provide a pattern that can help to determine the direction of fire travel or the fire origin

• Arrow patterns are the patterns left on wood structural elements– Point back toward the area of origin

• As the wood studs are subjected to flames and heat, they start to char – No exact science on burn time for wood studs

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Floors

• Patterns on the floor can be of great value depending on the circumstances

• Certain conditions must be considered– If the room went to flashover, then any previous

pattern may be destroyed

• Holes in the floor are always a safety concern – Can be created by heat and flame impingement on

the underside of the floor – Direction of fire travel can usually be determined by

looking at the burn pattern around the hole

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Carpets

Figure 11-15 Burnpattern on a carpetresulting fromthe presence of apoured ignitableliquid.

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Wood Flooring

• Charring or burning indicates a low burn • A small amount of an ignitable liquid with a short

burn time on a sealed hardwood floor may show whisping and sooting

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Concrete

Figure 11-16 Typicalspalling on concreteas the result ofmoisture in theconcrete expandingas it turns to steam,forcing the surfaceof the concrete toseparate from therest of the floor.

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Protected Areas

Figure 11-19Protected areaswhere schoolsbooks had been lefton the floor.

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Patterns on Furnishings

Figure 11-20 Lightdamage on akitchen chairshowing thedirection of firetravel is from theright to the left.

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Summary

• Finding and recognizing burn patterns aid the investigation

• Investigator may encounter heavy char and conflicting patterns

• In the event the fire went to flashover, the investigator is cautioned about burn patterns

• Patterns that look like they indicate an intentionally set fire must be thoroughly examined