AdBlue is a standardized, non-toxic diesel exhaust fluid (DEF) consisting of 32.5% high-purity synthetic urea and 67.5% deionized water. It is used in modern diesel vehicles equipped with Selective Catalytic Reduction (SCR) systems to dramatically lower harmful nitrogen oxide (NOx) emissions. The name AdBlue is a worldwide registered trademark owned by the German Association of the Automotive Industry (VDA), which guarantees that the fluid strictly adheres to international ISO 22241 quality standards.