Understanding natural gas emergencies


CarolinaFireJournal - Jason Krusen
Jason Krusen
01/11/2011 -

Natural gas related calls, whether for an odor of gas in the area, or an actual release, are a common call for almost every fire department across the county. The fire department or hazmat team is typically the first call made for assistance by the community, and depending on dispatch protocols the local gas company may be notified as well. A natural gas incident should be treated as a hazmat incident in addition to the suppression issue it may pose. It is the role of the first responders to handle it as such, and hopefully mitigate the incident before it progresses to the latter.

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Typically, these calls end without any incidents, and quite often are treated as though they pose no threat to the responder or the community. A lack of understanding and complacency will eventually lead to disaster. Well defined guidelines and proper training will help prevent incorrect operations by response personnel, and properly mitigate the leak.

There have been several recent events covered in the national media involving the true hazards associated with natural gas. Although not typical, the recent conflagration in San Bruno, Calif. shows a true worst case scenario of the potential threat natural gas has. On Sept. 9, 2010 a high pressure natural gas pipeline suffered a leak and eventually ignited explosively without warning. In the end, 37 homes were destroyed, nearly 300 others evacuated, and unfortunately seven civilians perished.

On Feb. 13, 2010, five firefighters were injured in a natural gas explosion inside a single family dwelling in Poland, Ohio. Crews responded to a report of a gas odor in the residence. Luckily, initial crews were equipped with atmospheric monitoring equipment, and used the equipment prior to entering the structure. The homeowners were sitting in their car at the neighbor’s house as a crew opened the front door and registered high readings on the meter. A separate crew was attempting to secure the gas meter when the home exploded.

On May 7, 2009, eight firefighters and one gas company employee were injured when a strip mall exploded in Forestville, Maryland. Workers in one of the stores called and reported a gas odor, which was originating from a vacant store adjacent to the caller. Firefighters evacuated all the businesses in the strip mall and waited for a gas company employee to secure the gas to the building. Firefighters were attempting to ventilate the gas filled structure when it exploded. Actual video footage of the incident is available to demonstrate the destructive force of the natural gas as it ignites. These are just a few incidents to emphasize the importance of treating natural gas emergencies with caution, and more importantly — being prepared.

Natural gas is a fossil fuel found naturally underground. It has been used in the United States for hundreds of years, but was not easily accessible via pipeline until the 1920s. Natural gas is mostly comprised of methane, a colorless and odorless gas. It may have small amounts of pentane, propane, and butane, which are usually refined out. Because it is highly flammable and odorless it posses a major safety concern, so an odorant is added. Methyl Mercaptan is added to assist the end-users in identifying it, and has rotten egg or cabbage smell. The odor threshold has been reported as low as .002 parts per million (ppm). Methyl Mercaptan in large enough quantities is highly toxic although only a few parts per billion (ppb) are added to natural gas, far below toxic levels.

Natural gas has a flammable range of five to 15 percent in air, and is non-toxic, although it is an asphyxiant. With the odorant added, it is noticeable long before it is close to being dangerous. Since natural gas is lighter than air it will rise rapidly when not confined inside a structure. It is very easily identified by its pungent odor, so identification even by civilians is quite common. If released under ground, it is known to travel hundreds of feet following natural fishers and voids around pipes. Following the path of least resistance it will present in the most unlikely locations. Therefore, do not dismiss complaints from neighbors who smell gas several houses away from the determined leak.

Natural gas is used in both residential and commercial properties. It is used for heating, water heaters, stoves, clothes dryers, fire places, outdoor lighting, and in industrial processes. The Energy Information Administration in a 2002 report showed 24 percent of the energy consumed in the United States came from natural gas. It is a common use of energy and will be encountered every where from a single family residence up to large commercial structures. Dependant upon the amount of gas and the pressures utilized, there are several gas meter configurations. Because of the differences it is important to pre-plan the various types of gas meters in your response area.

It is also a good idea to take note, or preplan the regulating stations in the area. These have built in safety features that prevent over pressurization of the lines. It is not uncommon to have a station that releases small amounts of natural gas that is smelled by the residents surrounding the area. If a leak can not be located, and nothing is found by responders, be sure to check the area for these stations. Although the leak may not be active now, it is quite possible it was the source prior to responders arriving. This process is completely normal and should not warrant action. If it continues to release, notify the gas company so they may check the valves and regulators. DO NOT attempt to isolate a valve. Responders should never attempt to isolate any valve above or below ground except for at the meter shut-off. The meter shut-off valve is located on the piping before it enters the actual meter.

Response to natural gas leaks can last from several minutes to several hours. Often the response time of the gas company is a large determining factor. Evaluate the hazards presented on the scene and provide the adequate resources to handle them. While an initial response to a report of a natural gas leak may warrant a full structural response resulting in five or six pieces of apparatus, it is acceptable to reduce this to one or two pieces once the scene is evaluated. A gas leak on a construction site with no life safety issues or structures threatened, is a good example of this. However, a gas leak inside a nursing home may require additional resources than what were dispatched.

The normal call is likely to begin with an initial dispatch of fire units to “an odor of gas.” This can go several different ways based on the initial information. It is extremely important to try and request additional information as soon as possible. An odor of gas reported could mean natural gas, liquefied petroleum gas (LPG), or gasoline — all presenting unique conditions. LPG and gasoline are heavier than air, presenting an additional safety concern for the responders. This article will focus solely on natural gas emergencies.

There are two common locations a leak will occur outside of a structure. The first is at the meter and is normally a small leak, unless an external force is used such as a vehicle running into the meter. If a leak is above the shut-off valve it can be handled with a spanner or pipe wrench by turning the valve a quarter turn. Another common exterior leak is a cut or broken gas line and typically occurs underground. These tend to be more difficult than a gas meter leak, but if properly prepared can be handled with limited resources. The first priority is to identify where the leak is coming from, and then isolate the area accordingly. Interview the workers if they were able to see the size of the pipe that was cut. Service lines are usually 5/8” plastic or 3/4” steel and mains are typically 2” and run as large as 6” or 8.” Natural gas lines are commonly cut by contractors and homeowners performing work near buried lines.

Anyone that is going to do any type of digging is required to have all utilities marked prior to doing any work; this includes planting trees and shrubs. Each state has a calling center but the center can be reached by calling the nationwide number, 811 “Call Before You Dig.” Depending on the state, it may take 48 to 72 hours before all utilities are marked, and the marking usually has an expiration of one to two weeks. There is a universal color code that is used to differentiate the type of utility.

Isolate the immediate area and deny entry. If machinery is left running around the leak do not attempt to turn it off. There is a risk of a spark during shut-down; it is safer to leave it running. Take into consideration the weather conditions and where the gas is going. On a hot and calm summer day the gas will rise rapidly into the atmosphere, while on a cool, overcast, and breezy winter day the gas may be pushed around.

Check the structures surrounding the leak and relocate those individuals if needed. Make sure any evacuated structure is monitored for natural gas once the leak has been isolated to check for trapped gas. Do not attempt to crimp a plastic (polyethylene) pipe, as the flow of gas through the pipe alone generates a static charge. Any additional bending or restriction in flow only increases the static build up. For this reason first arriving units should not attempt to isolate a leak by bending or crimping a gas line. Procedures to reduce static discharge and special crimping tools should be used. The gas company typically locates the cut line, and from a safe distance crimps a remote section.

Leaks inside of a structure pose a far greater risk than those outside. These calls should be handled not only with caution, but with the proper equipment. This begins by gathering as much information as possible from the dispatcher. Ensure that the callers have evacuated the structure while en route. Stage all apparatus at a safe distance, not parked in front of the structure in question. Interview those reporting the leak prior to entry to determine the following information:

  • Are all occupants are out of the structure?
  • Do any occupants feel ill?
  • What time was the odor first detected?
  • Is it localized or throughout the structure?
  • What appliances use natural gas?
  • Has there been any work in or around the structure or appliances recently?

Always use meters to check for gas prior to entering a structure. Your nose will only last a short time until it becomes desensitized or saturated. Always attempt to back-up or confirm the meters by using multiple meters. If dangerously elevated readings are encountered, exit the structure immediately, shut-off the gas meter, and wait until the gas company arrives. If low readings are encountered, an attempt to pin point the leak prior to shutting off the gas meter can be made if personnel are trained. It is quite possible a pilot light is out, or a specific appliance has an issue and can be isolated without shutting off all the gas to the structure.

This can be extremely helpful to the residents in the dead of winter if the problem is with the stove, and the heat is able to be left on. This should only be attempted if meters are used, and more importantly personnel are trained and comfortable using them. Once the gas meter is isolated it will be difficult to determine the source of the leak. Once a gas meter has been isolated it should only be turned back on by the gas company.

It is recommended that the fire department work with the local gas company to determine the actions to be performed by the fire department/hazmat team before incidents occur. Natural gas emergencies are a common call and like any other type of emergency, responders should be prepared to handle them. Walk through the common scenarios you are presented with and determine your ability to act, and more importantly what your department wants you to do. The local gas company is a great resource, so get to know them — and if possible, train with them.

Jason Krusen is a captain on Haz-Mat 1 with the Columbia Fire Department in Columbia, SC, with over 14 years of experience. Krusen is a Planning Manager with State Urban Search and Rescue Team, SC-TF1, a Logistics Manager for the Type II Collapse Search & Rescue Regional Response in Columbia, and a Planning Manager for the Midlands Region IMT. Jason is also the Project Manager and Instructor for E-Med Training Services, LLC.
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  11/27/2012 6:32:48 AM
Karsen 


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I reokcn you are quite dead on with that.



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