Skip to main content

Developed and maintained by the NFCC


Flammable or explosive atmosphere

Hazard Knowledge

The legal definition of a confined space includes a specified risk of 'serious injury due to fire or explosion'. This can arise from a flammable or explosive atmosphere being present.

Fire and rescue personnel need to appreciate that confined spaces as defined by regulation present a unique and hazardous environment. Before entering such areas, they must apply a dynamic risk assessment and should only commit personnel who have received confined space training.

Inappropriate ventilation of a flammable or explosive atmosphere may create additional hazards. Gas purging using inert gases is performed in industry to mitigate this risk, but would be inappropriate in confined spaces containing casualties.

A risk of fire or explosion can arise from:

  • Presence of flammable substances
  • Excess oxygen in the atmosphere
  • Presence of chemicals that can combust or spark in enriched (or, in some cases, normal) oxygen levels
  • Ignition of combustible dusts (see Operations- Physical hazards)
  • Leaks from adjoining plant or processes that have not been effectively isolated
  • Inappropriate ventilation