FAQ – Everything you Never Knew you Wanted to Ask About Odorization
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Odorization is the process of injecting an odorant into gas to make it detectable to a person who has an ordinary sense of smell.
The odorizer or odorant injection system is the equipment that infuses odorant into a gas stream. There are chemical injection and chemical vaporization systems. GPL manufactures odorant injections systems.
The odorant is the compound or chemical, often mercaptan, that is injected into the gas to make it detectable with its scent.
The odorant is likely to be a blend of different organosulfur compounds or even non-sulfur compounds. Common odorants for natural gas may include tertiary butyl mercaptan, tetrahydrothiophene, isopropyl mercaptan, dimethyl sulfide, and methyl ethyl sulfide.
Adding an odorant to undetectable gas began in Germany in the 1880s. However, it took a catastrophe on U.S. soil in 1937 to gain widespread odorization acceptance. At that time, a non-odorized gas leaked into a London Texas school, and over 300 people were injured, and more than 295 students and teachers killed.
Odorant is injected or infused into the natural gas stream to intentionally deliver the distinctive odor of rotten eggs or hydrogen sulfide, to warn people in the area that natural gas is present.
How much odorant is added to natural gas? Natural Gas is odorized so that a person with a normal sense of smell can detect it at a concentration that is well below the explosive range. The level of odorant may change depending on the applicable local codes; however, an odorant concentration between 0.5 to 1.0 percent by volume is typical.
The lower explosive limit (LEL) is the lowest concentration (by percentage) of a gas or vapor in the air that can ignite in the presence of an ignition source. Below the LEL, the gas is too lean to burn. For methane, the primary gas of natural gas, the LEL is 5%. Likewise, the upper explosive limit (UEL) is the highest concentration (by percentage) of a gas or vapor in air that can ignite in the presence of an ignition source. The UEL for methane is 15%. When above the UEL, the gas is too rich to ignite.