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In fire safety, stratification describes the dynamics, buoyancy and energy of smoke during combustion in large spaces where an energised plume of warm smoke rises above the source of a fire (being cooler and less dense than the surrounding air). In this circumstance, stratification can occur in one of two forms;

  1. the energised plume of smoke rises until it meets a layer of cooler air below the ceiling or roof in the space where the fire exists preventing the heat and smoke from rising further and inhibiting the normal operation of a point-type heat detector or smoke detector; or
  2. the process where an energised plume of smoke rises while its heat energy is heat energy dissipated as the plume rises. As this occurs, the upward movement of the plume gradually stops and the plume begins to spread horizontally in all directions. In some circumstances the plume may not reach the ceiling above, preventing the normal operation of a point-type heat detector or smoke detectors above.

Where the occurrence of stratification could occur consideration for supplemental methods of fire detection should be considered such as;

  • carbon monoxide fire detection;
  • flame detection;
  • aspirating smoke detection;
  • projected beam smoke detection at various levels;
  • video smoke detection.

In these circumstances the assistance of a competent fire safety engineer should be considered.


In preparing this definition, we have drawn from various sources including Legislation, Codes, Standards and industry information, research and knowledge.  Like the english language, these definitions may subtly change from time to time. As such these definitions are provided solely on the basis that users will be responsible for making their own assessment of the definition and and are advised to verify all relevant representations, statements and information.