Skip to main content

Developed and maintained
by the NFCC


Flammable or explosive atmospheres

Hazard Knowledge

When attending incidents within the petrochemical industry and fuel distribution network, fire and rescue service personnel may need to manage flammable or explosive atmospheres.

Some examples of these are:

Unconfined vapour cloud explosions (UVCE)

Large quantities of flammable gases or vapours in open air that are ignited and may cause deflagration with pressure waves or, less commonly, supersonic (detonation) advancement of flame fronts (e.g. ethylene vapour cloud).

Confined vapour cloud explosions (CVCE)

Flammable substances igniting in a container (e.g. process vessel) that generate pressure build-up and detonation velocities (e.g. natural gas explosions).

Boiling liquid expanding vapour explosions (BLEVE)

Caused by the failure of pressure vessels containing volatile flammable liquid and/or gases involved in fire.

Oil storage tank fire phenomena

  • Steam explosions
  • Boil over
  • Froth over
  • Slop over

For further information, refer to National Operational Guidance: Fires and firefighting.

Demolition or repair of tanks

Fire and rescue service personnel may encounter an explosion hazard from 'empty' tanks, which may contain an explosive mixture in the tank. This is because flammable vapours may be emitted when the sludge or residual contents are heated, e.g. from repair work, demolition, or radiated heat from a nearby fire.