SOP 209.02C HAZ-MAT NATURAL GAS INCIDENTS
Fire Department units may encounter natural gas in a variety of situations and incident types, each presenting a different set of hazards and problems. The following guidelines present an approach that will be applicable in the majority of situations, but do not replace good judgment and experience in dealing with any particular incident. The guidelines should be used whenever these types of situations are encountered.
Natural gas is much lighter than air and will dissipate rapidly outside. Inside buildings, however, it tends to pocket, particularly in attics and dead air spaces. The flammable limits are approximately 3% to 15% in air.
Burning natural gas should not normally be extinguished, since this changes the hazard from visible to invisible and creates an explosion hazard. Stopping the flow should control fires.
Units arriving at the scene of a structure explosion must consider natural gas as a significant possible cause. Explosions have occurred in structures that were not served by natural gas. Underground leaks may permit gas to travel considerable distances before entering a structure through the foundation, around pipes or through void spaces. In these circumstances the cause of the explosion may be difficult to determine. Until it can be determined that the area is safe from the danger of further explosions, evacuate all civilians and keep the number of Fire Department personnel in the area to a minimum.
Look for signs of a gas leak, i.e., smell of gas, flames coming through cracks in ground or around foundations, bubbling through puddles. Do not extinguish flames coming up through the ground.
Do not rely on gas odor. Odorant may be filtered out by passage through ground. Use Combustible Gas Indicators to check suspected areas.
Check systematically using combustible gas meters. Start close to area of explosion and take several readings. If gas is detected, increase the area until readings go to zero. Map the effected area.
Probe the ground for underground leaks. Use ground probe and check in any holes or caverns for pockets of gas. Inside structures, check around pipes, near cracks in foundations and in high portions of the building.
Always beware of the possibility of additional explosions. Shut off pilot lights and possible sources of ignition in the effected area, cut electricity from outside to avoid arcing. Ventilate buildings where gas in found.
Work the gas company personnel to pinpoint location of any leak. They can provide additional instruments to detect leaks.
Calls for "odor of gas," "gas leak," "broken gas line" and similar situations may range from minor to potentially major incidents. All of these should be approached as potentially dangerous situations.
The Hazardous Materials Plan, SOP 209.02, should be used as a basic guide for these incidents. A minimum number of personnel should be allowed to enter the area to size-up the situation while any additional units stage in a location out of the potentially dangerous zone.
Evacuate any civilians from the area of escaping gas.
Attempt to locate the source of gas and shut off devices available.
If the problem is an extinguished pilot light on an appliance, Fire Department personnel may relight the pilot after assuring there is no explosive accumulation in the area. In any other gas leak situation within a building, the gas supply shall be shut off and red-tagged until repairs are completed. This is most easily accomplished with the cooperation of the gas supplier at the scene.
If there is any indication of gas accumulating within a building, evacuate civilians from the structure and control ignition sources. Shut off electrical power from an outside breaker, check for explosive concentrations with a combustible gas indicator if there is any suspicion of accumulation within a structures Ventilate, using blowers to pressurize if necessary.
If gas company personnel must excavate to shut off a leak, firefighters shall provide stand-by protection with a charged 1-3/4” line, with the firefighters in full protective equipment.
All personnel working in the vicinity of a known or suspected natural gas leak shall wear full protective clothing. Personnel working in a suspected ignitable atmosphere (i.e., attempting to plug a leak in a gas line) shall USE SCBA and shall be covered by a charged protective hose line. The number of exposed personnel will be kept to an absolute minimum at all times.
A safety perimeter shall be established and maintained around any suspected gas leak.