What is a ceiling jet in the context of fire behavior?

A ceiling jet refers to the downward airflow created by the heated smoke layer at the ceiling during a fire. As a fire burns, it generates heat, causing the surrounding air and smoke to rise. This rising hot air eventually cools and begins to lose buoyancy, leading to a phenomenon known as the ceiling jet. As the hot smoke travels along the ceiling, it can spread out laterally and then ultimately descend, creating a flow of heated gases and smoke just below the ceiling level.

Understanding the nature of ceiling jets is critical for fire behavior analysis, as they can influence fire spread, smoke movement, and conditions within a burning structure. This concept helps investigators understand how fires behave in confined spaces, allowing for more effective fire suppression and evacuation strategies.