Wildland Fire Investigation, FI–210 Origin and Cause Determination

Light or no wind – origin closer to the center of the burned area
5-28 First Responder – Transition Zones
Transition zones can also help you identify the general origin area. Once the fire begins to
advance under the influence of slope or wind it burns with more intensity. There are a number of large,
“macro-scale” indicators that will help you locate the general origin area and possibly the actual point
of origin. Once you’ve learned these you should be able to answer the following four questions.
Fire Behavior
Identifying transition zones:
Changes in fire intensity
Point of slope or wind influence
• Macro-scale indicators Fire
direction indicators:
Angle of char in tree and brush crowns is steeper than the slope
Deeper charring on the sides of objects facing the approaching fire.
“Foliage-freezing” consistent with wind direction
Grass stems completely consumed in advancing areas; unburned and toppled to the ground in
backing areas with heads pointing toward the origin
5-29 First Responder – Question 1 (Refer to CD.) The angle of char on this tree crown is steeper than
the slope. Therefore, we know that this is an area of advancing fire.
On which side of this picture would the origin area be5-30 First Responder – Question 2 (Refer to
CD.) These downed logs show more damage on one side than the other. On which side of this picture
would the origin most likely be5-31 First Responder – Question 3
(Refer to CD.) This foliage crown is “frozen” in the direction the wind was blowing when the fire
passed it.
On which side of this picture would the origin most likely be
5-32 First Responder – Question 4
(Refer to CD.) This is most likely an area of backing fire spread. Advancing fire spread areas would
have an absence of grass stems. In which direction would the origin most likely be
5-33 First Responder – Basic Information