Determining the Determining the Point of OriginPoint of Origin

Why?• Required by State Law

• Prevent future fires

• Moral obligation

Before determining the point of origin

You must determine the

Area of Origin

Area of Origin

The geographic location of where the fire started

ex. kitchen

Point of Origin

The specific location where the heat source comes in

contact with the fuel

For a fire to occurFor a fire to occur

• You must have a heat source

• You must have a fuel

• You must have an act that brings the two together

Steps in Determiningthe “Area of Origin”

• Interview witnesses and firefighters

• Examine the exterior of the structure

• Examine the interior of the structure

• Analyze the information gathered

Step 1: InterviewStep 1: Interview

• Location, size, and appearance of the fire upon discovery?

• Any unusual circumstances before, during, or after the fire?

Step 2: Exterior Examination

• Supplements information gathered in interview

• Look for anything unusual

• Match exterior burn patterns with interior burn patterns

• ROT: heaviest auto vent stains are above the doors & windows of the room of origin

Step 3: Interior Exam

• Go to indicated area

• Work from areas of least damage to areas of greatest damage

• Evaluate the “indicators”– charring, V-patterns, light bulbs, window

panes, floor damage, and multiple areas of origin.

Indicators

Help guide the investigator in determining the point of

origin

Char

Material composed of carbon that has been

burned and has a blackened appearance.

Charring• Look for areas of lowest burning

• Check bottoms & underside of furniture

• Low charring indicates area of origin may be at a low level (caution: fall down)

• Study the entire pattern of damage, relate low burns to entire burn pattern

• Check depth of char.

• ROT: char is deepest near P.O.O.

More Charring

• Compare char depths of similar products

• Follow & diagram char patterns (least-most)

• Consider all information gathered so far.

Ceiling Damage

Most damage directly above the area of origin

Vertical Surfaces

The most charred sides of vertical surfaces usually face the direction from which the

fire approached

V-Patterns

The V-shaped burn pattern points close to or directly to the area of origin of that particular

pattern

Fall Down

Secondary fires caused by fall down have separate v-patterns.

Fall down occurs from convection or radiated heat.

V-Patterns

• Narrow V = fast burning

• Wide V = slow burning

• Burn patterns are dark or light depending on heat intensity & type of material

Light Bulbs

• Soften & Swell when exposed to heat

• Points toward the heat source

• Helps determine fire travel

• Vacuum filled bulbs (low watt or automotive bulbs)– sink in on the side closest to heat

source

Window Panes• Compare broken glass to glass left in

the pane

• Smoke stains?

• Location of broken glass?

• May indicate fire conditions– baked on = high heat

– loose soot = lower heat

Floor Damage• Usually damaged less than ceiling

– 20-30% of the ceiling damage

• Good indicator of area of origin

• Heavy char at or near area of origin

• Burn through may indicate additional fuel– ex. Chair, bed, couch, etc.

Spalling

Chipping or breaking away of the surface of concrete as a result of high temperatures

Causes of Spalling

• Moisture in concrete

• Green concrete

• Presence of an accelerate

• Closely examine concrete floors that have spalling

Multiple Areas of OriginMay indicate intentional

burning

Accidental fires may ignite items that give appearance of

multiple points of origin

Factors affecting fire spread

• Nature of combustibles in path

• Building features and layout– may assist or resist spread

• Ventilation drafts

Total Structural Loss

• You can’t save them all

• Reasons:– magnitude of fire

– duration of fire

– age of building

Total Fire Loss

• Black Holes, Grounders, Black Spots

• Burn indicators may not exist

• Information from witnesses, owner, and occupants can help determine the circumstances surrounding the fire loss

Remaining Contents

• Systematic examination can help determine– locations of contents before fire

– temperature differences among areas

– floor plans