When the fire is confined code as incident type:
Note: Confined fires that extend into the structure, cause significant cost and/or injury are structure fires 111 - Building Fire (or maybe 112 - Fire in a Structure other than a Building) … only code a confined fire for if the fire was confined to the heat holding equipment, without extension.
Note: Confined fires that remain in the heat holding equipment typically require less documentation; i.e. no fire module nor structure fire module. See the NFIRS guidance on how to code a confined fires and details on when more is needed.
When dealing with a structure fire, document as such (with fire and structure modules) and with the equipment being involved in ignition as the chimney or flue equipment.
See more NFIRS coding examples for quick “how to” coding snippets: