A Little Goes a Long Way
A little can go a very long way. Smoke and soot can travel a surprisingly long distance. Walking outdoors, you can tell by the odor if a neighbor is grilling, or has a fire in the fireplace or patio fire pit. The wind can carry smoke and soot from a grass fire for miles.
In your home or business, the soot and smoke can permeate through textiles, wood, walls, insulation and practically anything that is porous.
In this home the soot from a relatively small fire reached and affected the attic insulation. Other less severe methods can sometimes be effective to remove smoke odor, but to remove the soot in this situation required removal of the insulation.
All will be replaced soon to enable the occupants to get back to normal.