Selective catalytic reduction (SCR) inoshandiswa kudzora NOx mumagetsi edhiziri.NH3 kana urea (kazhinji urea aqueous solution ine mass ratio ye 32.5%) inoshandiswa sechinhu chinoderedza.Pasi pemamiriro ekuti O2 concentration inopfuura mirairo miviri yehukuru yakakwirira kudarika NOx concentration, pasi pekuita kweimwe tembiricha uye catalyst, NH3 inoshandiswa kuderedza NOx kuN2 uye H2O.Nekuti NH3 inosarudza kuderedza NOx pasina kuita neO2 kutanga, Naizvozvo, inonzi "selective catalytic reduction".