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.

From the production of odorant blends’ components to the odorant storages at consumption points, there is a broad and complex supply chain to bring the right odorant at the right place and at the right time, safely and without odor incidents. The transport and delivery of gas odorants can be achieved in many different ways:

• Odorants can be transported in 6,000 gallon ISO tank Containers for sea transport.
• On land, odorants can be transported by railcars, containing about 20,000 gallons, or by tank trucks, with typicalcapacities ranging from 250 to 6,000 gallons. The odorant has to be unloaded safely and without odor release, usually

  using a close loop vapor recovery system, from the supplier container into the storage tank of a gas utility.

• In addition, odorants can be packaged in returnable cylinders, with typical sizes ranging from 5 to 250 gallons returnable cylinders up to 660 gallons for semi-bulk containers (SBCs). These cylinders are designed to be connected to the odorant injection system via dry-break couplings and can be used as the odorant storage tank at consumption point. Once empty they are replaced by a full one and the empty cylinder is to be returned to the odorant supplier tobe refilled.
• Odorants can be packaged in one way drums from 1 gallon cans (pails) to 55 gallons drums, which have to be safelydisposed of once emptied.