All around the world, propane, butane and natural gas must be odorized. The odorization ensures a safe transport, distribution and use of this valuable energy to residential buildings. Regulations vary from one country or state to another. The natural gas can be odorized at different points of the gas grid: in some countries (France, Spain, South Korea…), odorization takes place at the entry points of the country’s gas grid, either at the gas transmission pipes or at Liquefied Natural Gas (LNG) terminals just after vaporization. In other countries (USA, Canada, Mexico, Germany, Italy, Belgium, China…), natural gas is often odorized at “city gate” level, where gas is depressurized to allow distribution to residential points.
Odorants also may vary from one country to another, and within the same country as well. The International Organization for Safety (ISO) is listing in the ISO 13734(1) components commonly used: odorants are mainly composed of Sulfides (TetraHydroThiophene, MethylEthylSulfide, DiMethylSulfide) and Light Mercaptans (mainly TertiaryButylMercaptan, IsoPropylMercaptan). With the exception of TetraHydroThiophene which can be used as a standalone odorant, odorants are composed of blends of these thiochemical compounds. By definition, these odorant are flammable products and have a very low odor detection threshold: 0.3 part per billion in volume for TertiaryButylMercaptan(2). Any small leak of odorant can trigger a misleading gas alert. A significant leak will do the same and may lead local authorities to evacuate large city areas to manage the public reaction and protect people against the potential fire and chemical risks.