Flammable Atmospheres

Flammable or Explosive atmospheres in the workplace can be caused by flammable gases, mists or vapours or by combustible dusts. Explosions can cause loss of life and serious injuries as well as significant damage.

An explosive atmosphere is defined as a mixture of dangerous substances with air, under atmospheric conditions, in the form of gases, vapours, mist or dust in which, after ignition has occurred, combustion spreads to the entire unburned mixture.

EN 1127-1 “Explosive atmospheres. Explosion prevention and protection. Basic concepts and methodology” lists the following potential ignition sources:

  1. Hot surfaces
  2. Flame and hot gases (including hot particles)
  3. Mechanically generated sparks
  4. Electrical apparatus
  5. Stray electrical currents, cathodic corrosion protection
  6. Static electricity
  7. Lightning
  8. Radio frequency (RF) electromagnetic waves from 104 Hz to 3 x 1011 Hz
  9. Electromagnetic waves from 3 x 1011 Hz to 3 x 1015 Hz
  10. Ionising radiation
  11. Ultrasonics
  12. Adiabatic compression and shock waves
  13. Exothermic reactions, including self-ignition of dusts

Dust explosions are documented separately on the Combustible Dust page.

This topic relates to the following PSM elements:

Risk Assessment
Operational Integrity

The Energy Institute has a number of publications associated with Hazardous Area Classification