Option 1. Our textbook suggests that if the liquid is at or above its flash point, the flame spread rate is fast, and the entire pool is engulfed within seconds. In such a case, the liquid is already evaporating sufficiently to reach the lower flammability limit in the vapor phase over the fuel surface. Can liquid burn if its ambient temperature is below its flash point? Why, or not?
Option 2. The authors of our textbook suggest that when a fire plume hits a ceiling, it spreads horizontally. Describe two reasons why the properties of the ceiling jet and the hot, smoky upper layer in a room are important. Do the ceiling jet and the upper layer differ? Why, or why not?