2014: Workers digging in Ewing, New Jersey, struck a natural gas line, causing a leak and resultant explosion that killed a resident, injured seven workers, leveled 11 homes, and caused at least some damage to all 130 homes in the development.
|Firefighters and other emergency personnel routinely respond to emergencies involving natural gas. (Photo by Pixabay.)|
2016: A gas leak in a basement meter room in a Silver Spring, Maryland, apartment building caused an explosion and ensuing fire that killed seven people. The dead-bolted front door of the apartment directly above the meter room was blown off and found 300 feet away, across the street in a parking lot.
2017: Workers in Manor Township, Pennsylvania, were investigating an odor of gas/gas leak outside a home and excavating a potentially leaking gas line near the home when an explosion occurred, killing one worker, injuring three other workers, leveling one home, and damaging several other homes.
2017: Two workers in Minnesota were removing existing piping to support the relocation of gas meters from the basement of a school building to the exterior of the building when a line under pressure was opened and not able to be shut down. As the building was being evacuated, an explosion occurred, killing two school employees and injuring nine other people. A fire and partial building collapse ensued.
2017: A natural gas explosion is suspected of leveling a Nebraska home and damaging more than a dozen others, causing the death of one occupant and critically injuring another. The couple were reportedly blown out of the house.
Firefighters and other emergency personnel routinely respond to emergencies involving natural gas. Such emergencies include residential fires, odors/leaks in buildings, damaged gas lines, or—the worst-case scenario—an explosion with ensuing fire.
Often, emergency responders arrive prior to the utility company and begin efforts to secure the scene. A basic knowledge of natural gas and how to eliminate or control hazards can make an incident run much more smoothly and, more importantly, ensure the safety of all personnel on scene. Firefighters must consider safety for themselves and the community first and foremost when responding to emergencies involving natural gas.
ABOUT NATURAL GAS
Predominantly methane, natural gas is colorless; tasteless; and, in its natural state, odorless. Transmission pipeline and utility companies add a distinctive odorant (butyl mercaptan) to natural gas so leaks can be quickly and easily identified. Natural gas is lighter than air (vapor density <1) and tends to rise, while most other flammable/energy gases have vapor densities >1 and tend to move downward.
Natural gas is nontoxic and considered a simple asphyxiant. Utility companies indicate that the natural gas mixture from the pipeline will typically have a lower explosive/flammable limit (LEL/LFL) of five percent and an upper explosive/flammable limit (UEL/UFL) of 15 percent. Five to 15 percent natural gas in air is considered the “flammable range.”
Natural gas typically originates in underground deposits and is extracted in a number of ways. Energy companies have also developed alternative processing methods to create natural gas and, currently, there is a “boom” in natural gas in North America, which has reduced gas prices and encouraged expanding use of natural gas. Transmission pipelines transport the natural gas at high pressures [up to 999 pounds per square inch (psi) www.aga.org/knowledgecenter/natural-gas-101] throughout the country to local natural gas utilities. These companies purchase the gas and distribute it to the customer through a distribution piping system.
Gas distribution systems operate at pressures ranging from ¼ psi to 99 psi and consist of mains, services, valves, and meters. In a gas distribution system, services and mains are constructed of steel, cast iron, ductile iron, wrought iron, or plastic, depending on the system age and type of service.
Natural gas transmission and distribution piping system installations must conform to rigid construction requirements set forth in ANSI B31.8, Gas Transmission and Distribution Piping System Standard. National Fire Protection Association 54, National Fuel Gas Code, contains requirements for the installation of natural gas piping and appliances inside buildings. The federal Department of Transportation (DOT) maintains jurisdiction over the safety of transmission pipelines. Distribution systems must also comply with DOT regulations as well as Public Utility Commission requirements.
Utility companies must ensure the integrity of their natural gas distribution systems through a comprehensive safety program that involves surveying, monitoring, maintenance, and testing. Most utility companies have responsibility for the distribution system up to and including the natural gas meter. Property owners are responsible for all natural gas piping inside buildings downstream of the meter. Many rural and suburban areas have no piped natural gas service. In these areas, the gas service may be bottled gas, such as liquid propane gas (LPG). The information contained in this article does not apply to LPG. Fire departments should be aware of where there is natural gas service in their coverage areas.
Here is guidance for handling incidents involving natural gas.
On scene. Immediately notify the utility company once you’ve determined an incident involves natural gas. Once they arrive on the scene, instruct utility company personnel to report to the incident commander (IC) or the liaison officer in a well-developed incident command system (ICS). Many utility workers receive ICS training to work within the system and can assist in evaluating the problem, recommend actions to take, and request additional resources as needed.
|The San Bruno pipeline explosion occurred on September 9, 2010, in San Bruno, California, a suburb of San Francisco, when a natural gas pipeline owned by Pacific Gas & Electric exploded into flames in the Crestmoor residential neighborhood two miles west of San Francisco International Airport. (Photo by MisterOh.)|
Gas detection. When dispatched to investigate an odor of gas, notify the utility company immediately. Utility company employees are trained and equipped with gas detecting instruments. Odors can come from many causes, including petroleum products such as gasoline, propane, marsh gas, sewer gas and industrial gases. Many fire departments now have access to flammable gas/lower explosive limit (LEL) meters. It is important to clearly understand what a meter reads and any limitations of that meter.
For some meters, high gas concentrations that result in an oxygen-depleted atmosphere may result in an inaccurate reading of the level of flammable gas and potentially a false low reading of LEL. Also understand that the LEL is a percent. For example, the LEL of natural gas is approximately five percent, meaning that if there is five percent of natural gas in a mix with 95 percent air, there is enough gas to result in a fire/explosion. In this case, if a LEL meter is being used, it will read 100 percent LEL at the five percent mix of natural gas in air. If the meter is reading 10 percent LEL, it does not mean that you are above the LEL; it is indicating that there is 0.5 percent of natural gas in 99.5 percent air. There may be variations in the actual concentration of gas in air because of meter calibrations (meters are typically calibrated to a specific calibration gas, and there may be some variation in reading in the field to a gas that is different than the calibration gas) and because of incomplete mixing of the natural gas in the space being metered (since it is lighter than air, natural gas may tend to collect in the upper spaces of a room/area or in other areas where air movement is incomplete).
Responding crews must attempt to identify the type of gas causing the odor and the source of the leak. Gas meters that read LEL need to be used to determine where the hot zone is. Firefighters must realize that any LEL reading on a meter (or the distinctive odor of gas) indicates the presence of gas and the potential for a hazard to exist and thus becomes part of the hot zone. Meters must be calibrated regularly to be effective and at a gas incident, if the fire department does not have a meter, it needs to be aware of where to get one and have it brought to the scene. When taking readings, it is always best to use two meters when possible to verify readings.
There is the possibility that an odor of “gas” could be something other than natural gas. It could be gasoline or could be odors from appliances that use various fuels. Although carbon monoxide itself does not have an odor, incomplete combustion of fuels can result in gases that may have an odor. Larger batteries of various types, including automobiles and backup power capabilities, can off-gas and present odors that occupants may confuse for natural gas.
Clearly understand the functions, limitations, and calibrations of the meters that you use. Review meter operational manuals, and get training on the proper use, calibrations, and applications for these meters from factory representatives.
ESCAPING NATURAL GAS OUTSIDE A BUILDING
Notify the utility company immediately if unignited natural gas is escaping from the ground from an excavation or from an open pipe outside a building. Establish a hot zone around the leak’s location. This hot zone should include any area where detection equipment indicates any gas reading (one percent or more).
|Firefighters investigating a reported odor of gas in this large home found an odor and meter readings inside the home and backed out. The meter was checked, and gas was noted flowing through it so they isolated the gas supply at the meter to await the arrival of the utility company. Investigation with representatives from the utility company determined that the odor was coming from a vehicle being charged in the garage, which was secured. The home was ventilated, the utility company restored the gas service, and the occupants returned to the home. (Photo by Greg Jakubowski.)|
Actions. Extinguish all flame and other ignition sources within this hot zone. Be aware that any electrical equipment, including that brought by the fire department to the scene, presents a possible ignition source if it is not rated for flammable atmospheres. Turning on or off any electrical equipment can create a spark and ignite leaking gas. Check surrounding buildings for any presence of natural gas odors. Reroute and restrict vehicular and pedestrian traffic from entering the immediate area until utility company personnel can bring the natural gas flow under control. If the leak continues, the hot zone may need to expand and must be continuously monitored. Do not try to bury the leak or use a master stream to disperse the gas. Either of these tactics may hinder operations and keep the natural gas low to the ground.
For any gas leak, any electrical equipment, including ventilation fans, radios, pagers, meters, and lights used in the hot or warm zone, should be appropriately rated for use in flammable atmospheres. A technical review of classified equipment is at www.ul.com/global/documents/offerings/services/hazardouslocations/CI_protection_methods.pdf.
NATURAL GAS BURNING OUTSIDE
When natural gas is burning, notify the utility company immediately. Only utility company personnel can operate valves on mains. However, emergency responders trained in the use of curb keys may close curb valves on natural gas services, but they should never turn on valves or curb valves. (Note: Restoration of gas service includes reignition of pilot lights, checking safety equipment associated with burners, and other tasks that require specialized training. Once something is shut off, leave it off. Turning the wrong valve or opening a closed valve could further endanger life or property. Leave these actions to utility company personnel.)
The best method to control an outdoor natural gas fire is to shut off the natural gas flow. In most cases, the emergency responder should not attempt to extinguish the fire while natural gas continues to escape as a risk of explosion could ensue. Establish and maintain a hot zone. If the natural gas fire has spread to exposed combustibles, a fire hose stream or extinguisher can be used to extinguish the exposed fires, using care NOT to extinguish the gas fire itself.
Do not fill an excavation where gas is leaking with water, as water could enter the gas main system. If it proves necessary to extinguish a natural gas fire before gas flow can be stopped, typically to perform a rescue for someone in imminent danger, then use dry chemical. Do this only as a last resort, because escaping unburned gas creates the potential for explosion.
For an uncontrolled gas leak with no ignition, evacuate everyone, including firefighters, from the immediate area using meters to monitor the extent of the hot zone as previously described.
ESCAPING NATURAL GAS IN A BUILDING
When escaping natural gas is found in buildings, notify the utility company immediately. Clear the building of occupants, including emergency personnel. The IC should determine if the natural gas can easily be shut off inside the building without risk to personnel or if it must be shut off at the outdoor meter/service, which should be equipped with a valve that can be shut off with a wrench. The best course of action is almost always a shutoff outside of the building.
It may prove extremely hazardous for firefighters to enter a building to shut off the gas inside. Ventilate the building by opening the doors and windows. Do not operate electrical switches, phones, or other equipment that could create sparks (including nonintrinsically safe radios and ventilation fans) in the hot zone. When ventilating a building, the initial scenario may be gas levels that are ABOVE the flammable range and, in the ventilation process, firefighters may bring the atmosphere down into the flammable range, which could result in an ignition. Do not be complacent if gas readings are high.
ESCAPING NATURAL GAS BURNING IN BUILDINGS
When escaping natural gas is burning in buildings, the IC should notify the utility company immediately and determine if the gas can be shut off inside the building or must be shut off at the outdoor meter.
In certain industrial or commercial buildings, turning off the natural gas might seriously interrupt important and costly processes or create further hazards. Preplanning these scenarios is extremely valuable, and the utility company and facility management can help determine the proper action. If the natural gas supply cannot be safely shut off, prevent fire extension by wetting surrounding combustibles with a fog stream until utility company emergency crews can control the flowing, burning natural gas.
INDOOR NATURAL GAS PIPING OR METERS
Notify the utility company immediately when it appears a fire endangers indoor natural gas piping or meter. The utility company is best equipped to shut off the supply of natural gas. The on-scene IC may elect to shut off the supply at an inside valve if it can be done safely.
In some rare cases, natural gas may burn out of control at an appliance. Notify the utility company when a natural gas-fueled appliance is involved in fire. You can typically control the fire by shutting off the gas flow at the appliance shut-off valve, if it can be safely accessed, or at the meter valve. Prepare to check for exposure fires behind and above the burning appliance. Do not turn on the appliance or meter valve once turned off.
GAS IN MANHOLES, VAULTS, SEWERS
Gas in sewers can come from a number of sources, including natural gas, propane, gasoline, sewage, and electrical cable burnout. The utility company can assist in identifying the type of gas involved and in tracing its source.
Do not attempt to extinguish flames if gas becomes ignited. Establish a hot zone around the opening, and keep vehicles and bystanders away from nearby manhole covers. Prohibit smoking and other potential sources of ignition.
Do not open manhole covers to investigate without consulting utility employees with specific expertise. Opening a manhole cover with a smoldering fire underneath can give similar results to opening the front door of a building with an oxygen-starved fire smoldering inside—presenting a backdraft situation. Always test the atmosphere of a manhole, vault, or sewer, first for oxygen levels and then for flammable gases, carbon monoxide, and hydrogen sulfide. Firefighters should not enter manholes, vaults, or sewers—leave that to utility personnel specifically trained to do so. In no case should anyone be allowed to enter a manhole if dangerous concentrations of gases or vapors are known or suspected and, if personnel enter, they must follow specific confined space entry procedures. At underground gas events, do not work or park over manhole covers/openings.
Check the basements of adjoining buildings for any evidence of gas intrusion. If found, ventilate by opening windows and doors. Shut off open flame devices, and do not operate electrical switches. If natural gas is involved, handle as suggested in the section on escaping gas in buildings.
When fire personnel must enter manholes, vaults, or sewers for rescue operations, follow confined space procedures.
EQUIPPED AND TRAINED
When under control, natural gas, like many other hazardous materials, is harmless. Natural gas is widely used for heating and air conditioning, water heating, cooking, incineration, drying, power generation, and many other commercial purposes in hotels, restaurants, schools, and many other occupancies. Natural gas is also widely used for thousands of industrial purposes every day. How we respond to emergencies involving this equipment can mean the difference between life and death for civilians as well as emergency responders. Having access to meters that are properly maintained/calibrated with personnel properly trained in their use is critical, as is having standard operating guidelines for response to gas emergencies.
Ensuring prompt notification of the utility company, isolating potential ignition sources, metering the immediate area and other areas where the gas could migrate, eliminating ignition sources (the utility company may need to cut electric power to the building for this), evacuating the area, establishing a hot zone (both explosion and collapse), ventilating the building as appropriate, and having rapid intervention crews available will keep both civilians and emergency responders safe. Contact your local utility company to determine what training it can provide on natural gas emergencies. Learning should never stop.
Note: Further tactical advice can be found at www.fireengineering.com/articles/print/volume-170/issue-4/features/natural-gas-emergency-strategy-and-tactics.html.
1. Davis, Mike, “Fatal Ewing gas explosion: PSE&G, contractor hit with largest fines in state BPU history,” NJ.com, March 2015, www.nj.com/mercer/index.ssf/2015/03/fatal_ewing_gas_explosion_bpu_issues_historic_fine.html.
2. Focht, Brian, “How to Respond to Natural Gas Emergencies,” FireRescue, September 2014, www.firerescuemagazine.com/articles/print/volume-9/issue-9/firefighting-operations/how-to-respond-to-natural-gas-emergencies.html.
3. Griffaton, Grace, “More details emerge on deadly home explosion in Manor Twp., Lancaster County,” Fox 43, July 2017, http://fox43.com/2017/07/05/more-details-emerge-on-deadly-home-explosion-in-manor-twp-lancaster-county/.
4. Johnson, Riley, “Jeanne Jasa, victim of house explosion, dies,” Lincoln Journal Star, August 2017, http://journalstar.com/news/local/911/jeanne-jasa-victim-of-house-explosion-has-died/article_9fa822a2-a058-5728-b88c-bf54033e9ded.html.
5. Uliano, Dick, “ATF locates disconnected vent pipe at scene of deadly Silver Spring explosion,” WTOP, August 2017, http://wtop.com/montgomery-county/2017/08/atf-locates-disconnected-vent-pipe-at-scene-of-deadly-silver-spring-explosion/.
6. Walsh, Paul, Libor Jany, and Miguel Otárola, “Hours after gas explosion at Minnehaha Academy, second body is found,” Star Tribune, August 2017, www.startribune.com/minnehaha-academy-dead-missing-gas-explosion-minneapolis-critically-injured/438110783/.
Brian Focht, CFPS, CFEI, is deputy chief of the Willow Grove (PA) Volunteer Fire Company and a senior training specialist with PECO, assigned to gas training at the PECO Fire Academy. He was the 2016 Recipient of the IAFC Garry Briese Safety Performance Award.
Greg Jakubowski, a fire protection engineer and certified safety professional, started his fire service career in 1978. He is a Pennsylvania state fire instructor and a former chief of the Lingohocken (PA) Fire Company. Jakubowski is also a member of the IAFC and a principal in Fire Planning Associates, a company dedicated to helping fire departments, municipalities, and businesses with preemergency planning.
To read more from Greg Jakubowski, visit www.firefighternation.com/author/greg-jakubowski.