FLAMMABLE GASES AND VAPOURS

EEHA & Hazardous Area Services Classification EEHA Services & Auditor Signoff Conformity Assessment Documentation Gases & Vapours Combustible Dusts Fitness for Purpose & Assessment Reports Flam & Comb Liquids Contact Details & Terms What's New

Flamable Gas & Vapour EEHA Inspection & Hazardous Area Classification

GASES AND VAPOURS

Gases and Vapours (and Mists) mix more or less homogeneously with air and form flammable mixtures relatively quickly.

While this is obvious for gases, vapours can travel very quickly and form flammable or explosive mixture with air in a very short time frame.

Some hydrocarbon liquids have lower explosion limits of not much more than 1% (which includes Unleaded Petrol) which makes there vapours particularly dangerous.

IGNITION TRIANGLE

Three things need to be present for gas or vapour in air mixtures to be flammable or explosive:

  • Sufficient fuel to be within the flammable range in air
  • Air (or sufficient Oxygen to allow ignition)
  • An ignition source of sufficient energy or temperature to allow ignition to initiate and continue.

Most explosion protection techniques work by removing at least one arm of the Ignition Triangle.

BUNCEFIELD VAPOUR IGNITON

The figure below depicts the aftermath of the Hemel Hempstead ULP release which suffered a remote area ignition of the ULP vapour, resulting in fires and ignition of the liquid ULP at the source of release.