What describes convection?

Convection is defined as the movement of heated gas or fluid in a circular pattern. This process occurs when a fluid is heated, causing it to become less dense and rise while cooler, denser fluid sinks. This creates a continuous flow pattern, often described as a convection current. In the context of firefighting and fire behavior, understanding convection is critical because it influences how heat and smoke travel during a fire, affecting visibility and conditions for both firefighters and victims.

The other options describe different methods of heat transfer. The first option pertains to conduction, where heat is transferred through direct contact between solid materials. The third option refers to conduction as well, emphasizing direct contact heating. Lastly, heating a vacuum does not facilitate any heat transfer because a vacuum lacks matter, making thermal energy transfer through convection impossible. Thus, the description of convection emphasizes the importance of fluid dynamics in the heat transfer process.