NFPA 921 states that the ______ should be used when conducting cause and origin investigations.

• A. Quick Surveys
• B. Ad Hoc Inquiries
• C. Systematic Investigations
• D. Guesswork

Answer: (C)

NFPA 921 directs investigators to use a systematic investigation when determining cause and origin. This means applying a structured, evidence-based, and repeatable approach rather than informal observations or unplanned inquiries. In practice, a systematic investigation involves planful scene assessment, careful preservation and collection of physical evidence, and the use of fire science principles to develop and test hypotheses about ignition sources, fuels, and the sequence of events. Findings are documented clearly, alternate explanations are considered, and the process is designed to be reproducible by others so conclusions are credible and defensible. Quick surveys, ad hoc inquiries, and guesswork lack the rigor and documentation needed for a reliable determination, which is why a systematic investigation is the appropriate method.