What is the impact of a flash fire's short duration on combustible materials inside a building?

The choice indicating that combustible materials inside a building may catch fire due to the short duration of a flash fire is accurate because flash fires can produce extremely high temperatures very quickly, even if their duration is brief. During a flash fire, materials that are already combustible or that have low ignition points can ignite rapidly when exposed to these intense temperatures.

The short duration does not imply that materials are immune to ignition—in fact, the rapid increase in heat can be enough to lower the ignition threshold of various items within the environment, leading to ignition. While some materials may resist catching fire under certain conditions, the nature of a flash fire poses a significant risk of ignition to combustible materials present.

In contrast, the other choices do not accurately reflect the behavior of combustible materials during such an event. The notion that they are completely safe is misleading, as safety is contingent on various factors including the presence of flammable materials and the nature of the fire itself. Saying they are unaffected overlooks the reality that even brief exposure to high heat can cause significant fire risk. Lastly, the idea of having a high ignition threshold is not necessarily applicable, as many typical combustible materials can have relatively low ignition thresholds that may be surpassed during a flash fire scenario.