What is a ceiling jet?

A ceiling jet refers to a relatively thin layer of flowing hot gases that develops under a horizontal surface, such as a ceiling. This phenomenon occurs during a fire when hot gases rise from the fire source and spread out horizontally upon reaching the ceiling. The ceiling jet plays a significant role in fire dynamics, as it influences how heat and smoke travel within a structure, affecting visibility and the temperature distribution in the upper layers of the room.

Understanding the concept of a ceiling jet is essential for fire investigators and safety personnel. It helps them assess potential fire spread, evaluate smoke behavior, and determine how the fire might affect occupants and structural integrity. The ceiling jet can also be a critical factor in designing fire suppression systems and planning evacuation routes, as it can significantly impact conditions in the upper atmosphere of a room where occupants may need to navigate.