Which fire stage is defined by exhausted fuel supply or an oxygen level dropping below 16%?

Which fire stage is defined by exhausted fuel supply or an oxygen level dropping below 16%?

• A. Incipient
• B. Growth
• C. Decay
• D. Fully Developed

Answer: (C)

The stage described is decay. In this phase the fire is winding down because almost all the available fuel has been consumed or the air is so oxygen-depleted that combustion slows dramatically. When oxygen drops below about 16 percent, the flame becomes less intense and the heat release declines, often leaving behind smoldering embers and heavy smoke rather than large flames. This shift means the fire may seem to be dying out, but hazards remain: hidden pockets of heat can reignite if air and fuel mix again, and ventilation changes can trigger rekindling or backdraft conditions. In short, decay is defined by fuel exhaustion or critically low oxygen leading to diminished flames and heat, with continued risk from residual embers and altered air flow.

The stage described is decay. In this phase the fire is winding down because almost all the available fuel has been consumed or the air is so oxygen-depleted that combustion slows dramatically. When oxygen drops below about 16 percent, the flame becomes less intense and the heat release declines, often leaving behind smoldering embers and heavy smoke rather than large flames. This shift means the fire may seem to be dying out, but hazards remain: hidden pockets of heat can reignite if air and fuel mix again, and ventilation changes can trigger rekindling or backdraft conditions. In short, decay is defined by fuel exhaustion or critically low oxygen leading to diminished flames and heat, with continued risk from residual embers and altered air flow.