This document discusses common myths and misconceptions about fire investigation techniques. It notes that factors like depth of charring, size of alligatoring blisters, presence of spalling or annealed springs cannot reliably indicate duration or use of ignitable liquids on their own. Narrow burn patterns, window crazing, or tripped breakers also do not prove arson on their own. The document advocates following NFPA 921 guidelines, obtaining certification, thoroughly documenting investigations, and being certain before ruling a fire incendiary. Fire investigators are legally responsible to investigate all fires using careful scientific methods rather than unverified theories from the past.

1. Fire Investigation Myths and Fire
Investigator Responsibilities
Tom Bohm, Fire Marshal
Hermiston Fire and Emergency
Services

2. Char /Alligatoring

3. Myth #1 Depth of Char / Alligatoring
• Myth – An investigator could estimate how long
the fire burned by the depth of the char
• Truth- Charring shows time or intensity – Low
intense fire/long duration may have the same
char pattern as a high intense pattern/short
duration
• Use char as an indictor of fire travel

4. Myth #1 Depth of Char / Alligatoring
• Myth - Alligatoring- if the blisters were large and
shiny a sign of ignitable liquid was used
• Truth- There is no significance to alligatoring

5. Spalling

6. Myth #2 Spalling
• Myth- Spalling in concrete means ignitable
liquids were used
• Truth – the area beneath a puddle of liquid, even
ignitable liquids, will be cooler than adjacent
exposed surfaces during a fire

7. Annealed bed or furniture springs

8. Myth #3 Annealed Bed or Furniture Springs
• Myth- Caused by a long duration smoldering
event- cigarette in a sofa
• Truth- Short duration exposure of over 750° F
causes annealing
• Can be used to quantitate fire flow and intensity

9. Ignitable liquid / pour pattern

10. Myth #4 Ignitable Liquids/ Pour Patterns
• Myth – Narrow or irregular burn patterns on the
floor are reliable signs of an ignitable liquid
• Truth- not reliable in post flashover fires or in
drop down fires
• Worn carpet areas may show a pattern
• Furniture padding may melt

11. Myth #5 Spontaneous Combustion
• Myth- Stain rags in a pile will spontaneously
combust
• Truth- pile has to be just right- too tight and no
oxygen and to loose heat dissipates
• Remember – these stain give off ignitable vapors

12. Myth #6 Electrical Fires
• Myth- the absence of tangible proof of an
incendiary fire indicates electrical caused fire
• Truth- Sometimes you just have to say the fire is
ruled accidental and the cause is undetermined
and then state why

13. Myth #7- Fire are Ruled Arson or Suspicious
• Myth - The fire is ruled arson or suspicious
• Truth- Arson is a crime – no one has been
convicted
• Truth- No fire is suspicious – suspicious is a
level of proof not a classification of cause- only
accidental, incendiary , natural or undetermined

14. Windows

15. Myth #8 Windows
• Myth – greasy windows indicate a petroleum
product was used
• Truth- greasy windows mean nothing
• Myth- Crazing of glass proves rapid, intense fire
• Truth- proves rapid cooling- crazing can occur
with a 140° F temperature change or difference

16. Smoke Patterns

17. Myth #8 Color of Smoke/ Intense Fast Fires
• Myth- Black smoke means a petroleum based
ignitable liquid was used
• Truth – Not a reliable indicator
• Myth- Fast fires are caused by ignitable liquids
• Truth- 1977- it took 17 minutes from the sounding of
the smoke alarm to flashover,
In 2009 – 3 minutes • Wood and gasoline burn at same flame temperature

18. Tripped electrical breakers

19. Myth #8 Tripped electrical breakers
• Myth- Tripped breaker meant an electrical fire
• Truth- Tripped breaker may mean temperatures
at panel at over 400° F for over 20 minutes

20. Myth #9 Burn Patterns
• Myth- Charring on the bottom of the door
indicates ignitable liquid was used
Truth- This usually happens when the door is
closed and hot gasses escape

21. Is Fire Investigation “Junk Science”
• Myth- what I was told in 1977 by fire
investigators is it true today
• Truth- most fire investigators at that time used
experience and what other older fire
investigators said for their fire investigation
methodology and theories
• Truth- Fires can be inconsistent – too many
variables, wind, humidity, size of room, oxygen,
ceiling height, fuel load

22. How to Improve Fire Investigations
• Training
▫ NFPA 921
▫ National Fire Academy
▫ IAAI
• Certification
▫ NFPA certification through DPSST
▫ CFI through the IAAI
• Use a systematic approach to fire investigation everytime
▫ Pictures
▫ Sketches
▫ Outside to inside, least burned to most burned fire
investigation method – everytime
▫ Document, Document, Document

23. How to Improve Fire Investigations
• You need to rule in as well as rule out
• Not one single indicator can be taken at face
value without considering other factors
• Unless you are certain – the fire is undetermined
• Do not make your investigation fit your theory
• To be classified incendiary it must be “ beyond a
reasonable doubt of fire investigator certainty”

24. Basic Responsibilities for Fire Investigations
• Understand- that by state law fire departments are
responsible to investigate every fire
Depositions are not FUN
Know
▫ NFPA 921- Guide for Fire and Explosion Investigation
▫ Amendment IV – unreasonable search and seizure
▫ Amendment V – Due process of law
▫ Amendment VI – Speedy trial, counsel

25. Basic Responsibilities for Fire Investigations
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Michigan v. Tyler – reasonable period of time
Michigan v. Clifford- search warrant
Fire investigators- interview
Spoliation of evidence
Chain of custody
Documentation
Types of evidence – Demonstrative,
Photograph/Illustrative, and Testimonial

26. Basic Responsibilities for Fire Investigations
• Testimonial Evidence▫ Fact witness
▫ Expert witness
 Federal rules of evidence
 Daubert v. Merrell Dow