DU0-001 · Question #156
What are the three stages of combustion? (Choose three.)
The correct answer is A. Incipient. Incipient (A) correctly names the first of the three classic stages of combustion: Incipient, Free-burning, and Smoldering. These are the recognized phases fire passes through from ignition to dying out. The distractors are wrong for these reasons: Back draft (B) is a dangerous…
Question
Options
- AIncipient
- BBack draft
- CThermal flux
- DIntense heat
- EVisible smoke
How the community answered
(17 responses)- A76% (13)
- B12% (2)
- C6% (1)
- D6% (1)
Explanation
Incipient (A) correctly names the first of the three classic stages of combustion: Incipient, Free-burning, and Smoldering. These are the recognized phases fire passes through from ignition to dying out.
The distractors are wrong for these reasons:
- Back draft (B) is a dangerous fire phenomenon caused by sudden oxygen introduction - a fire behavior event, not a combustion stage.
- Thermal flux (C) refers to the rate of heat transfer through a surface - a physics/heat measurement concept, not a stage.
- Intense heat (D) describes a characteristic or condition that may occur during combustion, but is not a named stage.
- Visible smoke (E) is a byproduct observable across multiple stages, not a stage itself.
Memory tip: Think "I Fire Slowly" - Incipient, Free-burning, Smoldering - to recall all three stages in order from ignition to near-extinction.
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