AdBlue^® is a highly purified colourless liquid. It contains demineralized water and urea (32.5%). It is used with diesel engines and is also known outside of Europe as DEF, ARLA 32 or AUS 32 in some countries. 

AdBlue® is used with diesel engines using SCR technology. This technology (Selective Catalytic Reduction) reduces harmful emissions (NOx). AdBlue® is injected into the catalyst of the SCR system, where it triggers a chemical reaction with the ammonia. This chemical reaction converts the toxic nitrogen oxides (NOx) into nitrogen (N2) and water vapour (H2O). Water vapour and nitrogen are naturally occurring gasses that are harmless to the environment.