What type of combustion occurs when materials burn from underneath?

Subsurface combustion occurs when materials ignite and burn from underneath the surface. This type of combustion is particularly relevant in firefighting, as it can happen in situations where there are layers of materials, such as mulch, that can smolder and burn beneath the surface, making it challenging to detect and extinguish.

Understanding subsurface combustion is crucial for firefighters because it often requires specific tactics to effectively extinguish, as the fire may not be visible on the surface. It can also lead to deeper and prolonged fires that may adversely affect structures and the environment, requiring firefighters to consider factors like air access and the types of materials involved when planning their attack.

In contrast, surface combustion refers to flames that are visible on the surface of the fuel, while flash combustion is characterized by a rapid and explosive reaction to a heat source, often occurring quickly when the conditions are right. Smoldering combustion, on the other hand, occurs without visible flames and is often associated with burning debris that can still pose a threat if not properly managed.