Minimum Ignition Energy

Minimum Ignition Energy

• MIE depends on type of gas and concentration
• 8.0% volume methane is "sweet spot" for stoichiometric combustion of methane
• Although flammability range for CH4 is 5 - 15%, concentration where it is easiest to ignite is 8% by volume
• At 25° C, 1.0 atm, takes 0.3 mJ to initiate explosion chain reaction
• Static electricity "zap" when insert key into ignition = 5.0 mJ
• MIE for other combustible gases much lower

Combustible sensor electrical safety and performance requirements

• Important standards defining combustible sensor performance:
  • Canadian requirements: CSA 22.2
  • United States: UL 913
  • ATEX: EN50018
  • Harmonized IECEx: IEC60079-1