What minimum percentage left smoldering creates rekindle risk?

• A. 5 Percent
• B. 10 Percent
• C. 1 Percent
• D. 15 Percent

Answer: (C)

During overhaul, the danger comes from hidden embers that can stay hot enough to reignite when air and fuel are present. Even a tiny amount of smoldering left behind can pose rekindle risk because it may be in concealed pockets—behind siding, inside wall cavities, or under insulation—where heat persists and can flare up once disturbed or exposed to fresh oxygen. That’s why the minimum threshold isn’t a large amount; about 1 percent of left smoldering is enough to create rekindle risk. The takeaway is to treat any remaining heat as dangerous and continue thorough cooling, probing, and extinguishing until all hotspots are eliminated.