RIA NFPA 921 Fire Investigation 3 — Questions and Answers
Question 1: NFPA 921 classifies fire causes into which four categories?
- Accidental, natural, incendiary, and undetermined (Correct answer)
- Electrical, chemical, mechanical, and human error
- Arson, accident, lightning, and equipment failure
- Intentional, unintentional, act of God, and unknown
Correct answer: Accidental, natural, incendiary, and undetermined
NFPA 921 defines the four fire cause classifications as accidental, natural, incendiary, and undetermined.
Question 2: When is it appropriate for an investigator to classify a fire cause as 'undetermined' per NFPA 921?
- When witnesses are unavailable for interview
- When the evidence does not support any single cause classification (Correct answer)
- When the fire destroyed all physical evidence
- When insurance policy exclusions apply
Correct answer: When the evidence does not support any single cause classification
NFPA 921 states undetermined is appropriate when collected evidence is insufficient to support one cause classification to a reasonable degree of certainty.
Question 3: Which laboratory analysis technique does NFPA 921 recommend for identifying ignitable liquid residues in fire debris?
- X-ray fluorescence (XRF)
- Gas chromatography–mass spectrometry (GC-MS) (Correct answer)
- Scanning electron microscopy (SEM)
- Fourier-transform infrared spectroscopy (FTIR) only
Correct answer: Gas chromatography–mass spectrometry (GC-MS)
GC-MS is the ASTM E1618-standard method recommended in NFPA 921 for identifying ignitable liquid residues in fire debris samples.
Question 4: Per NFPA 921, which of the following is NOT a reliable indicator of accelerant use?
- GC-MS positive result from debris sample
- Pour patterns on flooring
- Unusual fire spread speed reported by witnesses (Correct answer)
- Low burn patterns inconsistent with fuel load
Correct answer: Unusual fire spread speed reported by witnesses
Witness perception of unusual fire speed is subjective and unreliable; physical and laboratory evidence are the accepted indicators of accelerant use.
Question 5: In NFPA 921, the 'area of origin' is defined as:
- The room where the most damage occurred
- A general geographic location within the fire scene where the fire began (Correct answer)
- The exact point where the ignition source contacted fuel
- The space with the highest concentration of accelerant residue
Correct answer: A general geographic location within the fire scene where the fire began
The area of origin is a broader geographic location such as a room or floor where the fire started, distinct from the more precise 'point of origin.'
Question 6: Which ASTM standard governs the collection and preservation of fire debris samples for laboratory analysis?
- ASTM E1459
- ASTM E1388
- ASTM E1492 (Correct answer)
- ASTM E1618
Correct answer: ASTM E1492
ASTM E1492 provides the standard practice for receiving, documenting, storing, and retrieving evidence in a forensic science laboratory.
Question 7: According to NFPA 921, which of the following fire scene observations is most indicative of a natural cause fire?
- Multiple unconnected areas of origin
- Lightning strike evidence on a structure (Correct answer)
- Accelerant odor at the scene perimeter
- Disabled smoke detectors found at the origin
Correct answer: Lightning strike evidence on a structure
Physical evidence of a lightning strike, such as char tracks on structural elements or ground strike marks, supports a natural fire cause classification.
RIA NFPA 921 Fire Investigation 3
NFPA 921 classifies fire causes into which four categories?