Properties of Natural Gas 

You may someday have to deal with natural gas at an incident scene. So, it’s important to know a few basic facts about natural gas, its properties, and how it behaves.

  • Natural gas is lighter than air.
  • It will follow the path of least resistance and will rise. Be alert. Natural gas will travel upward through any available space: stairwells, ducts, a crack in the road. It can even seep up through soft ground.
  • When underground or in enclosed spaces, gas will move laterally or migrate. It will travel as far as it can under roads, along utility lines and trenches, or along a ceiling, until it finds a way up.
  • Chemical additives produce the familiar sulfur-like smell of natural gas. Natural gas has no smell of its own.
  • Treated gas is referred to as “odorized.”
  • A lit cigarette is enough to ignite natural gas.
  • Natural gas has an explosive or flammable concentration range between about 4 percent and 14 percent gas to air. A 10 percent gas-to-air mixture is ideal for clean burning.
  • At concentrations below 4 percent or above 14 percent, natural gas will not burn. While gas should always be treated as highly flammable, in fact, it will only burn within this flammable concentration range.
  • Burning natural gas will not explode.
  • Liquefied gases have different properties than natural gas. Emergencies involving propane and butane may require different precautions and procedures than those covered in this program. Refer to departmental SOPs for these liquid gases.