Unit 4 – Sources of Ignition and Fire Patterns

Unit 4 Seminar Topics  Common sources of ignition Burn and smoke patterns Tips for the Investigator FS 301- Unit 4: Sources of Ignition and Fire Patterns

Lightning There are a variety of ignition sources. Some of them are listed below. Radiant Heat Smoking Materials Common Sources of Ignition Matches Lighters Brakes and Rotors Mufflers Catalytic Converters Electrical Components Sparks

Chimneys, Fireplaces and Wind  Chimneys and fireplaces are also ignition sources If construction is improper or chimneys are not used properly can they be involved in an unwanted fire ○ Prefabricated chimneys became a problem for homes built in the early 1980’s  The wind can have a serious effect on both chimneys and sparks It can cause a down draft, possibly blowing sparks into a room The wind may blow across the top of the opening of the chimney creating a strong updraft. This is known as the Bernoulli effect. FS 301- Unit 4: Sources of Ignition and Fire Patterns

Spontaneous Combustion FS 301- Unit 4: Sources of Ignition and Fire Patterns Ignition sources may be due to the spontaneous combustion of materials – Drying oils such as linseed oil, tung nut or fish oil, are all susceptible to spontaneous heating The reaction is dependent on the percentage of the oil that is in contact with oxygen along with its ability to dissipate heat – Self-heating of hay or straw is well-known as a spontaneous ignition source – The evaporation of moisture and fermentation by microorganisms causes heat release

Toaster Oven Microwave Oven FS 301- Unit 4: Sources of Ignition and Fire Patterns Appliances Appliances may be ignition sources – Misuse and abuse of small appliances may cause failures that result in fire Toaster ovens are easily ignited when misused Portable heaters have been a serious problem, especially in the workplace Small appliances can also be used to set fire intentionally using timers

Burn and Smoke Patterns Burn and smoke patterns are the indicators left behind after a 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 originates

Wood Framing Wood framing provide a pattern that can help determine the direction of fire travel or the fire origin – Arrow patterns are left on the wood structural elements. It points back toward the area of origin – The wood studs begin to char as they are subjected to flames There is no exact science on burn time for wood studs

Wall Surfaces Wall surfaces such as wallpaper and wood paneling are also helpful in providing a pattern that can help determine the direction of fire travel or the fire origin – Wallpaper with a plastic film on the surface burns differently from other types of paper surfaces – Wood paneling can burn away quickly but if stopped in time it can show a great cone (v) pattern) Wood Paneling Wall Paper

Doors An open or closed door can provide investigators with information on the burn pattern of a fire – An open door at the time of a fire and the V pattern will be evident on the surface of the door – A closed door will have hinges that charred on one side of the door The lack of a V pattern on the outside of the door indicates that the door was closed at the time of the fire

Windows and Glass Burn patterns on windows and glass patterns can be examined for clues to a fire’s development – 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 (with the exception of some energy efficient windows and plexiglass)

Floors Patterns on the floor can be of great value depending on the circumstances – If the room went to flashover, then any previous pattern may be destroyed – Holes in the floor are always a safety concern They can be created by heat and flame impingement on the underside of the floor The direction of fire travel can usually be determined by looking at the burn patterns around the hole – Spalling of concrete results from moisture expanding in the concrete FS 301- Unit 4: Sources of Ignition and Fire Patterns

Furnishings Furnishings may also provide information on the burn pattern of a fire – Light damage to a kitchen chair shows the direction of the fire travel from right to left – Heavy charring on the sofa points to higher heat on the left side FS 301- Unit 4: Sources of Ignition and Fire Patterns

Tips for the Investigator  Form a hypotheses and use good science to develop and challenge all hypotheses to find the cause of a fire.  Identification of the heat source must be done scientifically and accurately.  Research and uncover information about all aspects of the potential heat source.

See You Next Week  Work on…  Contact me if you have any questions FS 301- Unit 4: Sources of Ignition and Fire Patterns