Twin Specialties' line of diesel exhaust fluid (DEF) are colorless, non-flammable and non-toxic to humans and animals. It is recommended for use in most 2010 and later on- road and off-road diesel trucks, cars and stationary diesel engines requiring 32.5% DEF. In 2010, the EPA introduced stringent regulations to that required diesel engine vehicles to significantly reduce the level of harmful NOx emissions and particulate matter. Diesel exhaust fluid (DEF) chemically reduces NOx emissions by converting them to harmless nitrogen and water by way of injection directly into the engine exhaust stream before the SCR catalyst.