Harmless synthetic solution of urea, which is used as an AGENT FOR REDUCING TOXIC NITROGEN OXIDES IN THE EXHAUST GAS OF HEAVY DUTY DIESEL ENGINES ACCORDING TO SCR AND NSCR TECHNOLOGY. The treatment of exhaust gases with this agent leads to the conversion of toxic oxides into non-toxic products; nitrogen and water and thereby lead to a significant decrease in the concentration of nitrogen oxides in the exhaust gases.