Gas Leak - Leak Grades

Leak Grades

Most state and federal agencies have adopted the Gas Piping and Technology Committee (GPRTC) 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 SMYS, or greater, in a class 3 or 4 location, 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.