As a service provider to the general public, fire departments are called upon to investigate gas odors these days. Most of the time these incidents can be classified as minor in nature and very little effort on the fire department's behalf will be required. Other times, however, we can find the situation to be more involved and require a great deal more of our resources.
As a service provider to the general public, fire departments are called upon to investigate gas odors these days. These odors more than likely come from a natural gas appliance or the pipelines supplying the appliance. Most of the time these incidents can be classified as minor in nature and very little effort on the fire department's behalf will be required. It can be as simple as the pilot light on an appliance being out. Generally, the local utility company will have a service representative respond and check the service as well as relight the pilot. Other times, however, we can find the situation to be more involved and require a great deal more of our resources.
Transmission Pipelines are used to convey natural gas from storage or production facilities to the local utility company. The pressure within the Transmission Pipeline has the potential of reaching 1200psi in most cases. Once the utility company receives the natural gas for distribution, the pressure will be lowered to accommodate its intended use. Under normal usage pressures seldom exceed 150 psi for high pressure distribution and generally are more around the 60 psi range, found in residential settings. A grid system is used by the utility company for distribution of the natural gas throughout their service area. This grid system is known as the Distribution Pipeline or Main Pipeline. Off this grid system, Service Laterals or Lines, deliver the natural gas to the customer.
Newer homes and small businesses have a low pressure gas meter located on the outside of the structure; however, it is not uncommon to find gas meters inside some of the older homes and businesses. Inside meters will be equipped with a vent pipe extending outside the structure. In the event of a malfunction, the gas is vented to the outside atmosphere. Every meter, will have a shut-off valve located on the supply side which is known as a stopcock, requiring one-quarter turn to shut off the flow of gas. Some larger services employ a standard valve as a shut off. Most low pressure service lines and all high pressure services will have an underground shut off valve at the street. On high pressure installations, a regulator is installed ahead of the meter to reduce the pressure for suitable use by the customer. Firefighters should have the knowledge and skills to shut off valves at the meter, however, only the utility company should shut down the valve at the street location.
Natural gas is not poisonous as it contains no significant amounts of carbon monoxide or for that matter any other toxic gases. Therefore, we can safely say that it has no toxic effect on human beings. However, if the concentration levels of natural gas start to exceed 25% in a confines space area it will start too displace most if not all the air in that space along with the oxygen. Due to the lack in oxygen, one can suffocate.
Natural gas is naturally occurring, largely hydrocarbon gas, recovered from wells. Natural gas is mostly methane, with lesser amounts of nitrogen, ethane, propane, and traces of butane, pentane, carbon dioxide and oxygen. The mixture can range from 72% - 95% methane and 3% - 13% ethane, less than 1% - 4% propane and less than 1% - 18% nitrogen. This combination makes natural gas lighter than air; having a vapor density that ranges between 0.59 and 0.72.