It is not uncommon for unburned pyrolysis products to flow out of the area of initial involvement, mix with air, and ignite - EXTENSION.
Properly maintained opening protection is essential to containing the fire until suppression activities have been initiated. The inspector must ensure nothing has been done to nullify the protection of openings.
Protection of OpeningsFPT 102 - Fire Prevention and Inspection // Instructor: Kevin M. Kolb Slide #1