What Makes Natural Gas Smell? Understanding Odorants

As a manufacturer of natural gas odorizers, we often receive inquiries about the distinctive smell associated with natural gas. In this article, we’ll explore the role of odorants, specifically mercaptans, in making natural gas detectable by our sense of smell.

Odorants: Making Natural Gas SmellThe Odorization Process

Why Is Natural Gas Odorless?

In its unprocessed form, natural gas is odorless. However, an odorant is intentionally added to the gas because it is highly combustible. This ensures that individuals with an ordinary sense of smell can detect its presence.

Meet Mercaptans: The Key Odorant

Mercaptans (Thiols), a colorless and flammable gas, is the most common odorant used in natural gas. Its smell is often described as a mix of rotting cabbage and rotten eggs. When you encounter this odor, your instinct is to leave the area – and that’s precisely the intended effect.

Safety Measures and Awareness

Alerting People to Gas Presence

The primary purpose of gas odorants like mercaptans is odorization for safety. By alerting people to the presence of flammable gas, we prompt them to take necessary actions. Whether it’s evacuating the area or troubleshooting, this early warning system ensures your security.

Safety Information

Mercaptans safety information:

  • Description: A colorless gas with an extremely unpleasant odor.
  • Toxicity: Mercaptans can affect the central nervous system at very high concentrations.
  • Odor Threshold: Detectable well below dangerous levels (odor threshold of 1 ppb).
  • OSHA Exposure Limit: The Permissible Exposure Limit for mercaptan is ten ppm.

Remember, understanding these details is crucial for your safety awareness.

Common Odorants for Natural Gas

In addition to mercaptans (thiols), the following odorants play a crucial safety role by making gas leaks detectable. Their specific smells help individuals recognize the presence of flammable gas, prompting necessary actions. Safety awareness is essential; understanding these odorants contributes to a safer environment.

Mercaptans (Thiols):

  • Odor Description: Mercaptans smell unpleasant, often described as rotting cabbage or rotten eggs.
  • Safety: At very high concentrations, mercaptans can be toxic and affect the central nervous system. However, the penetrating odor associated with mercaptans is detectable well below dangerous levels. The gas has a smell at an odor threshold of 1 ppb, and OSHA has a Permissible Exposure Limit for mercaptan of 10 ppm.

Tert-Butyl Mercaptan (TBM):

  • Odor Description: TBM has a fruity or berry-like smell.
  • Safety: TBM is an effective odorant that alerts individuals to gas leaks. Its toxicity is similar to mercaptan’s, but its odor threshold ensures early detection.

Ethyl Mercaptan:

  • Odor Description: Ethyl mercaptan has a strong, garlic-like odor.
  • Safety: Like other odorants, ethyl mercaptan is detectable at low concentrations. It is commonly used in propane gas to make leaks noticeable.

Propyl Mercaptan:

  • Odor Description: Propyl mercaptan smells similar to rotten onions.
  • Safety: Its odor threshold ensures timely detection. It is used in specific gas blends for enhanced odorization.


Next time you catch a whiff of that distinct odor near a gas line, know it’s mercaptans doing its job – keeping you safe and aware. For more information, check out our FAQ on gas odorization.

  • zia

    Mixing of odorant oil is based on by pass odorization system (vaporization) for dry natural Gas
    TBM=80% CAS 75-66-1
    MES=20% CAS 624-89-5
    PRESSURE range 50-300 psig,temp 0F-100F & Specific gravity 0.6 -0.7
    Now the requirement is 90,000 kg. Can you please help us in this regards.

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