What phenomenon occurs when gases on the ceiling ignite?

The phenomenon that occurs when gases on the ceiling ignite is referred to as rollover. Rollover is characterized by the ignition of superheated gases that have accumulated near the ceiling in an enclosed space. As a fire burns, it produces hot gases that rise and collect at the top of the room. When these gases reach a temperature that is sufficient to ignite, they can combust, often creating a visible flame that rolls over the ceiling. This phenomenon is a critical indicator of a fire's growth and can signify that conditions are reaching a state of flashover if the fire continues to develop.

Understanding rollover is essential for fire inspection and firefighting strategies, as recognizing the signs can help firefighters determine the intensity of the fire and the associated risks.