NFPA 921 Fire Investigation Flashcards

Under NFPA 921, what is the investigator's responsibility regarding the fire scene before evidence collection begins?

Answer: Conduct a systematic scene survey and document conditions as found

NFPA 921 requires a systematic scene survey to document conditions before any debris is moved or evidence collected, preserving the evidentiary context.

In NFPA 921, 'char' is defined as:

Answer: The carbonized surface of a material that has been exposed to heat or fire

Char is the carbonized, blackened surface layer of a combustible material resulting from exposure to heat and fire, and it is a key indicator in origin determination.

Which type of container does NFPA 921 recommend for fire debris samples suspected of containing ignitable liquids?

Answer: New, unlined metal cans with friction-fit lids

NFPA 921 and ASTM E1412 recommend new, unlined metal paint cans with friction-fit lids to prevent contamination and vapor loss from debris samples.

What is 'fire behavior' as described in NFPA 921, and why is it important?

Answer: How fire develops and spreads, governed by physics and chemistry, informing origin determination

Understanding fire behavior—how fire grows, spreads, and interacts with its environment—is foundational to accurately interpreting fire patterns and determining origin.

Per NFPA 921, which condition can cause 'irregular burn patterns' on floors without the presence of an accelerant?

Answer: Burning furniture or falling combustibles creating localized intense heat

Burning furniture, falling debris, and other combustibles can create irregular floor burn patterns that mimic accelerant pour patterns without any ignitable liquid being present.

In NFPA 921 fire investigation, what is the 'neutral pressure plane'?

Answer: The horizontal level in a fire compartment where incoming air and outgoing hot gases are in equilibrium

The neutral pressure plane separates inward-flowing cool air below from outward-flowing hot gases above, influencing smoke and fire movement patterns.

According to NFPA 921, which of the following best describes an 'incendiary fire'?

Answer: A fire deliberately set under circumstances where the person knows the fire should not be set

NFPA 921 defines an incendiary fire as one intentionally set under circumstances where the actor knows it should not be set, distinguishing it from accident or negligence.