Gas Leak

 A gas leak refers to an unintended leak of natural gas or another gaseous product from a pipeline or other containment into any area where the gas should not be present. Gas leaks can be hazardous to health as well as the environment. Even a small leak into a building or other confined space may gradually build up an explosive or lethal concentration of gas.[1] Leaks of natural gas and refrigerant gas into the atmosphere are especially harmful due to their global warming potential and ozone depletion potential.[2]

Leaks of gases associated with industrial operations and equipment are also generally known as fugitive emissions. Natural gas leaks from fossil fuel extraction and use are known as fugitive gas emissions. Such unintended leaks should not be confused with similar intentional types of gas release, such as:

gas venting emissions which are controlled releases, and often practised as a part of routine operations, or

"emergency pressure releases" which are intended to prevent equipment damage and safeguard life.

Gas leaks should also not be confused with "gas seepage" from the earth or oceans - either natural or due to human activity.

Pure natural gas is colorless and odorless, and is composed primarily of methane. Unpleasant scents in the form of traces of mercaptans are usually added, to assist in identifying leaks. This odor may be perceived as rotting eggs, or a faintly unpleasant skunk smell. Persons detecting the odor must evacuate the area and abstain from using open flames or operating electrical equipment, to reduce the risk of fire and explosion.

As a result of the Pipeline Safety Improvement Act[3] of 2002 passed in the United States, federal safety standards require companies providing natural gas to conduct safety inspections for gas leaks in homes and other buildings receiving natural gas. The gas company is required to inspect gas meters and inside gas piping from the point of entry into the building to the outlet side of the gas meter for gas leaks. This may require entry into private homes by the natural gas companies to check for hazardous conditions.

In the United States, most state and federal agencies have adopted the Gas Piping and Technology Committee (GPTC) standards for grading natural gas leaks.

A Grade 1 leak is a leak that represents an existing or probable hazard to persons or property, and requires immediate repair or continuous action until the conditions are no longer hazardous. Examples of a Grade 1 leak are:

Any leak which, in the judgment of operating personnel at the scene, is regarded as an immediate hazard.

Escaping gas that has ignited.

Any indication of gas which has migrated into or under a building, or into a tunnel.

Any reading at the outside wall of a building, or where gas would likely migrate to an outside wall of a building.

Any reading of 80% LEL, or greater, in a confined space.

Any reading of 80% LEL, or greater in small substructures (other than gas associated sub structures) from which gas would likely migrate to the outside wall of a building.

Any leak that can be seen, heard, or felt, and which is in a location that may endanger the general public or property.

A Grade 2 leak is a leak that is recognized as being non-hazardous at the time of detection, but justifies scheduled repair based on probable future hazard. Examples of a Grade 2 Leak are:

Leaks Requiring Action Ahead of Ground Freezing or Other Adverse Changes in Venting Conditions. Any leak which, under frozen or other adverse soil conditions, would likely migrate to the outside wall of a building.

Leaks requiring action within six months

Any reading of 40% LEL, or greater, under a sidewalk in a wall-to-wall paved area that does not qualify as a Grade 1 leak.

Any reading of 100% LEL, or greater, under a street in a wall-to-wall paved area that has significant gas migration and does not qualify as a Grade 1 leak.

Any reading less than 80% LEL in small substructures (other than gas associated substructures) from which gas would likely migrate creating a probable future hazard.

Any reading between 20% LEL and 80% LEL in a confined space.

Any reading on a pipeline operating at 30 percent specified minimum yield strength (SMYS) or greater, in a class 3 or 4 location,[clarification needed] which does not qualify as a Grade 1 leak.

Any reading of 80% LEL, or greater, in gas associated sub-structures.

Any leak which, in the judgment of operating personnel at the scene, is of sufficient magnitude to justify scheduled repair.

A Grade 3 leak is non-hazardous at the time of detection and can be reasonably expected to remain non-hazardous. Examples of a Grade 3 Leak are:

Any reading of less than 80% LEL in small gas associated substructures.

Any reading under a street in areas without wall-to-wall paving where it is unlikely the gas could migrate to the out-side wall of a building.

Any reading of less than 20% LEL in a confined space.