The History and Importance of Natural Gas Odorant

Introduction

Natural gas and propane power homes, businesses, and industries across North America, providing an efficient and reliable energy source. However, these gases are naturally colourless and odourless, making them undetectable in their pure state. To ensure public safety, odorants—specifically mercaptans—are added to these gases as a critical safety measure. For less than a dollar per year per customer, this simple yet vital step prevents catastrophic accidents by making gas leaks easily recognizable. The history of natural gas odorization is marked by a tragic event that reshaped safety regulations worldwide, reinforcing the necessity of odorants in natural gas and propane distribution.

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The New London School Explosion: A Turning Point

One of the most devastating events in gas history occurred in 1937 in New London, Texas. An undetected natural gas leak in the school’s heating system led to an explosion that killed nearly 300 students and teachers. The gas, which was odourless at the time, accumulated unnoticed until a spark in a shop class ignited the air, levelling the school.

The catastrophe prompted swift regulatory action. Within weeks, Texas mandated that all natural gas must be odorized. The rest of the United States and Canada quickly followed suit, ensuring that a similar tragedy would never occur again. This incident remains a powerful reminder of the life-saving importance of odorants in gas safety programs.

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Odorant as a Safety Measure

Odorants are chemical additives mixed with natural gas and propane to create a distinctive smell, ensuring early leak detection. Because natural gas is naturally odourless, adding an odorant enables people to detect leaks at just 1/5 of the lower explosive limit, significantly reducing the risk of explosions or poisoning.

Importantly, odorants do not alter the chemical or physical properties of the gas—only its smell. The odorization process typically takes place before distribution, ensuring that all delivered gas meets stringent safety standards.

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Sulphur-Based Odorants

The main odorants used in natural gas safety are sulphur-based odorants. The most common odorants are mercaptans and sulphides, which have a strong, pungent smell resembling rotten eggs.

For an odorant to be effective, it must:

• Be detectable even at low concentrations.
• Produce no toxic byproducts.
• Remain chemically stable under various conditions.
• Not react with pipelines or other system components.

Some widely used odorants include tetrahydrothiophene (THT), dimethyl sulphide, diethyl sulphide, methyl ethyl sulphide, ethyl mercaptan, propyl mercaptan, and butyl mercaptan. Each type offers unique characteristics tailored to specific applications in the gas industry.

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Considerations for Selecting Odorant Blends

When choosing the right odorant blend, two primary factors must be considered:

1. Soil and Water Composition – In some cases, gas leaks from underground pipelines may have their odour stripped out by the surrounding soil and water. The ability of soil and water to absorb odorants depends on factors like composition and moisture levels.
2. Atmospheric Humidity – Humidity levels affect how odorants behave in the air. In regions located in the center of a continent, colder winter temperatures, alkaline soil, and dry air can impact odour retention. In contrast, coastal areas typically have less alkaline soil, higher humidity, and milder temperatures, which influence how odorants disperse and persist.

At Tansley Associates, we are experts in odorant and can help you select the right odorant blend for your application and location.

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Regulations and Requirements

Today, strict regulations govern the use of odorants in natural gas and propane systems. All provinces in Canada and states in the U.S. mandate that domestic gas supplies be odorized. Globally, nearly every gas distribution system follows similar safety measures.

Federal regulations require:

• Detectable odorants in all distribution pipelines.
• Odorized gas in transmission lines within populated areas.
• Special monitoring systems to maintain proper odorant levels.

These regulations help ensure that gas leaks can be quickly identified and addressed before they pose significant risks.

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Safety Measures and Leak Detection

The distinctive, rotten egg smell of odorized natural gas and propane serves as an immediate warning of a potential leak. If a gas odour is detected, follow these critical safety steps:

1. Alert all occupants and evacuate the building immediately.
2. Avoid using electrical switches, matches, or open flames, as they can ignite gas.
3. Call the gas utility and fire department from a safe distance.
4. Only return to the building once authorities confirm it is safe.

Never assume that a gas leak is harmless—prompt action can prevent dangerous situations.

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Tansley Associates: Expertise in Odorant Services

At Tansley Associates Environmental Services, we are leading natural gas odorant suppliers, specializing in odorant supply, equipment, service, and maintenance across Canada and the United States. Our expertise ensures that gas utilities and distributors maintain compliance with safety standards while delivering properly odorized gas to customers.

If your organization requires expert guidance on odorization, Tansley Associates is ready to assist. Contact us today to learn more about our odorant solutions and ensure your gas systems remain safe and compliant.