At refineries, a complex combination of processes take place, converting the raw materials into high value products. The most fundamental refining process is distillation which separates the raw materials into various streams defined by their boiling points. The distillate streams are then further processed to remove any unwanted components, such as acids, sulphurs and metals, before they are selectively blended to yield the desired products. The blending ratio of these streams is the main difference between the Jet A and Jet A-1 grades. At this point additives are injected into many products to improve fuel performance and stability in order to meet the requirements of the different specifications. Jet fuels have a typical boiling range of 150-270°C, (which is somewhere between the boiling ranges of the gasoline and diesel we use in our road vehicles), and typically account for around 10-15% of total refinery production (3000 tonnes per day for a medium to large refinery!). However, actual yields are largely dictated by the quality and composition of the refineries feedstocks, and the demand for other fuels in that market.