In 1937, the unauthorized use of non-odorized gas at a New London Texas school caused a tragic explosion and fire that killed 294 people, both students, and teachers. Following the accident, federal authorities came together and determined that injecting odorous chemicals would help prevent a similar event from happening in the future. These regulations currently require gas companies to inject sufficient odorant such that a person with a normal sense of smell can readily detect a natural gas leak.

Natural Gas Odorants

Before understanding the process behind gas odorization, it’s important to review the common types of natural gas odorants. Since natural gas is completely undetectable by the human nose, chemical compounds are added to gas streams to create an odor. The most common odor associated with natural gas is “rotten eggs”, which is often attributed to the chemical mercaptan.

In its organic state, mercaptan has chemical properties similar to natural gas, making it a versatile odorant. However, depending on the application and particular environment, gas companies may use odorant blends of various organic sulfur and non-sulfur compounds. These may include tertiary butyl mercaptan, tetrahydrothiophene, isopropyl mercaptan, dimethyl sulfide, and methyl ethyl sulfide.

Gas Odorization Technology

Natural gas distribution companies consider ambient temperatures, soil conditions, and pipeline age when selecting the best odorant blends for their area. Because they are extremely concentrated, and because even the slightest leaks can lead to a large number of gas leak reports, liquid odorants must be handled properly. Many odorant manufactures will deliver the chemicals by truck or transportable containers designed to eliminate any leakage. 

Within the natural gas industry, there are three odorant injection technologies:

• Wick Style – Odorant is allowed to saturate a specially-designed wick suspended in a gas stream; odorant evaporates into the stream at a fixed rate.  Wick-type odorizers are generally used in smaller applications where gas flow is relatively constant. 
• Drip System – Odorant is gravity-fed through a needle valve and drips into the gas distribution pipe. The rate of flow is usually computer-controlled and varies by the amount of gas flowing in the pipe. 
• Injection System – Odorant is injected into the gas pipe using an electrical pump or pneumatic pump. The injection rate is also computer-controlled and varies as the gas flow increases or decreases. 

Pro Tip: Learn the correct terms! An odorant is the type of chemical being injected into the gas stream, and an odorizer is the type of equipment used for the process.

Monitoring Odorant Levels

To adhere to federal regulations, gas companies must maintain detectable gas odorization levels at one-fifth of the lower explosive limit. Proper monitoring of odorant levels is critical, as too little odorant provides insufficient protection, and too much can result in widespread gas leak calls by industrial and residential consumers. GDS Corp offers two families of odorant monitors to protect your gas pipelines:

• GDS-68SXP Advanced Natural Gas Odorant Monitor – Advanced remote odorant monitor designed for unattended, low-power operation. Supports automatic calibration, remote satellite monitoring and more.
• GDS-68XP Natural Gas Odorant Process Monitor– Process monitor designed to measure H2S. mercaptans and other gases in process flow applications. Uses low-cost electrochemical sensors and minimizes the amount of gas released into the environment. 

Protect Your Employees and Equipment 

Gas odorants play a critical role in protecting customers’ lives by ensuring that natural gas leaks are detected and repaired before hazardous conditions exist. Whether it’s injecting gas odorants, or monitoring gas odorant leaks around gas odorizing equipment, it’s crucial for your facility to have a reliable gas detection system.

Connect with our sales team to find a detection system customized for your specific environment.

Gas distribution companies must adhere to strict regulations to ensure the safe use of natural gas since it is highly combustible and odorless. Mercaptan compounds, tetrahydrothiophene (THT), and dimethyl sulfide (DMS) are among the most popular chemicals added to natural gas. Both the sulphuric elements and versatility of mercaptan make it a highly effective odorant. Learn more about this fuel additive to help you guard against potential gas leaks.

That Rotten Egg Smell

If you regularly work with natural gas, you’re probably accustomed to the “rotten egg” smell of gas odorants. While the specific odor may vary slightly based on the type of odorant, most gas companies strive to create a universal smell. Mercaptan compounds, specifically, contain the sulfur and hydrogen compound, hydrogen sulfide (H2S) to create a distinctive aroma unlike any other. 

Versatility of Mercaptan

Mercaptan is a non-toxic substance that is made of carbon, hydrogen, and sulfur. Because it’s regularly found in nature as a waste product for both animals and humans, mercaptans are also organic and extremely foul-smelling. That being said, mercaptans provide a number of advantages for industrial purposes.

• Low Requirements – Small amounts, specifically less than one part per million, of mercaptan, are necessary for human detection.

• High Performance – As a non-corrosive and nontoxic sulfuric compound, mercaptan can be applied in a number of ways.
• Similar Properties – In a gaseous state, mercaptan has chemical properties similar to natural gas and will evaporate in the same manner.

Other Types of Additives

Depending on your specific application, chemical compounds may be used singularly (like tetrahydrothiophene) or as a mixture with other compounds to create a gas odorant. The types of additives available may vary based on your location and specific industry, but will likely include these compounds:

• Dimethyl Sulfide
• Isopropyl Mercaptan
• Methyl Ethyl Sulfide
• Normal Propyl Mercaptan
• Secondary Butyl Mercaptan
• Tertiary Butyl Mercaptan
• Tetrahydrothiophene

It’s important to inject the appropriate amount of gas odorant to give natural gas a detectable smell. A small concentration of mercaptan compounds could put your safety at risk and excessive levels may result in costly service calls for suspected leaks.

Pro Tip: Not all gas odorants smell the same, making it essential for manufacturers to install a complete gas detection system to monitor concentration levels.

Safe Gas Odorant Monitoring

If you are a gas company that regularly distributes natural gas streams to homes or businesses, it’s crucial to have a reliable monitoring system. GDS Corp offers a number of natural gas odorant monitors to help you maintain optimal levels of mercaptan and THT odorants in your gas streams.

Connect with our sales team to find a gas distribution solution to meet your specific needs and applications.