Characteristics of Gaseous Fuels

Hydrogen, methane and propane are all capable of being ignited by relatively small sparks from shorted wires, static discharge or electric motor operation. Characteristics of each are presented in the table below.

Hydrogen: Odorless and lighter than air, it will disperse unless contained. It can be generated by battery charging (for more information about batteries and fire, click here)

Methane: Also known as natural gas, it is odorless by itself, but when manufactured it often has a rotten egg odor added to aid detection. Methane is lighter than air.

Propane: Propane by itself has a sweet odor, but often has an added odor of rotten egg to aid detection in the event of a leak. Propane is heavier than air and will gather in low areas if released.

Autoignition (oF) Flammability Range (%) Minimum Ignition Energy (mJ) Vapor Density (air=1)
Lower Upper
Hydrogen 932 4 75 0.019 0.1
Methane (natural gas) 999 5 15 0.28 0.6
Propane 842 2.1 9.5 0.25 1.6

The course section on Alternative and  Hybrid Vehicles will further explore vehicles with gaseous fuels.

References

  1. NFPA 921, Guide for Fire and Explosion Investigations, 2017 Edition.
  2. NFPA 497, Recommended Practice for the Classification of Flammable Liquids, Gases, or Vapors and of Hazardous (Classified) Locations for Electrical Installations in Chemical Process Areas, 2021.
  3. NFPA 325, Guide to Fire Hazard Properties of Flammable Liquids, Gases and Volatile Solids, 1994.