What is odor fade? What causes odor loss in odorized natural gas?

 In Natural Gas Odorization, Odorization Services & Products

What is odor fade? While smelling natural gas is the first warning that there is a gas leak, it is not foolproof. One of those reasons is the diminishing odor of odorized gas. Here are reasons you may NOT smell the odorant in gas during a gas leak.

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Natural Gas Odorization

Gas companies odorize natural gas (i.e., inject odorant into the gas) so that people can smell it for safety reasons. The process of natural gas odorization, particularly with an odorant injection system, provides an accurate injection of the correct amount of odorant. However, at times the gas does not smell, and while the tendency may be to look at the odorizer as the cause, there are pipeline conditions and other circumstances that may impede smelling the odorant in gas.

Odor Fade

natural gas pickling to odorize natural gas

Equipment “pickling” a natural gas pipeline to odorize the gas. Photo courtesy of Pipeline Conditioning.

Odor fade is a condition where there is a loss of odorant in the gas stream to such a level that the gas becomes undetectable. In this case, the odorant compound may decompose and change composition, or the odorant may be physically removed or pulled from the gas. In any case, there is a significant loss of odor. These are mostly chemical processes of either adsorption, absorption, or oxidation and occur in generally new gas pipe installations. While odor fade is more common in new large diameter steel pipes of long pipelines, it can also happen in shorter and smaller diameter PE (polyethylene) lines.
Other situations that may cause odor fade are:

  • During some gas leaks, the odorant may strip from the gas when seeping into some soils or concrete.
  • Rust, moisture, liquids, or other foreign substances in the pipe can create a loss of odorant.
  • Some odorizers cannot correctly odorize during low or intermittent gas flow conditions, causing odor fade.

Gas companies routinely perform pipe pickling to prepare the new pipelines before use. This process is also called pipeline conditioning or pre-odorization. If your company needs natural gas pipe pickling or pipeline conditioning, request a quote here.

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Odor Loss

odor loss or odor fade

Odor fade or odor loss? They’re different!

There are other conditions causing odor loss, and while they are not “odor fade,” they present the risk of failing to smell natural gas odorant.

  1. Olfactory Fatigue – Olfactory fatigue, or odor fatigue, occurs when prolonged exposure to a specific compound occurs. It is usually temporary and customary for people who work around natural gas odorants. In these cases, the person may be unable to recognize that odorant is present or that there have been changes in the odor level. Employers are encouraged to have gas detectors in these cases where their employees are routinely exposed to odorants.
  2. Smell Disorders – When someone suffers from anosmia, they are unable to smell, and those with hyposmia have a diminished capacity to smell. In either case, the sufferer may likely be unable to detect the odorant injected into gas.
  3. Sleeping – People in deep sleep stages will likely not smell odorant in a gas leak.
  4. Odor Masking – Odor masking occurs when one or more gas stream compounds can change, reducing the perceived odorant smell. In this case, the odorant may still be present, but the scent has changed.

There are always gas detectors and other measures to keep you safe for those with a smell disorder or those concerned about odor fatigue, odor masking, or concerns of failing to smell while sleeping.

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