What is defined as 'flashover' in the context of live fire training?

Flashover is defined as a rapid spread of fire that occurs when combustible materials in an enclosed space ignite simultaneously, resulting in a sudden and intense increase in fire intensity. This phenomenon typically happens when the thermal energy from a fire increases the temperature of the nearby materials to their ignition points.

In the context of live fire training, understanding the concept of flashover is crucial as it represents a significant safety hazard. Trainers must recognize the signs of impending flashover, such as a decrease in visibility and an increase in heat, to ensure the safety of all participants during training exercises. Recognizing and preventing flashover can help instructors create a safer training environment and better prepare trainees for real-world firefighting situations.

The other choices do not accurately represent the phenomenon of flashover; therefore, they lack relevance in this context. A gradual increase in fire intensity does not encapsulate the simultaneous ignition aspect of flashover. Techniques to start fires and methods to extinguish them are also unrelated to the specific and dangerous nature of flashover events.