In NFIRS-5.0 the data element Factor Contributing to Ignition (Block P20 of the Fire Module) is defined as the “circumstance or condition that allowed the heat source and the item first ignited to come together to start the fire (e.g., mechanical failure, misuse of material, operational deficiency).” Therefore, this field—not the others—records the specific mechanism by which the heat source contacted the first-ignited material.

A. Cause of ignition – Classifies the fire as intentional, unintentional, act of nature, etc.; does not describe the physical interaction of heat source and fuel.

B. Equipment involved in ignition – Identifies the equipment that generated heat or electrical energy; it does not capture how contact with the first-ignited item occurred.

D. Item first ignited – Codes the material/object that first caught fire; it records what burned, not the circumstances of contact with the heat source.

1. U.S. Fire Administration, National Fire Incident Reporting System (NFIRS) 5.0 Complete Reference Guide, Section “Fire Module,” Table P20 Factor Contributing to Ignition, definition paragraph (January 2021), pp. 126-127.

2. NFPA 921: Guide for Fire & Explosion Investigations, 2021 ed., §6.3.5 “Factors Contributing to Ignition,” pp. 40-41 (clarifies role of contributing factors in bringing heat source and fuel together).