The present invention relates to a process for producing 1-chloro-3,3,3-trifluoropropene, comprising the step i) of contacting hydrofluoric acid (HF) in a reactor with a starting composition comprising at least one of the chloro compounds selected from the group consisting of 1,1,3,3-tetrachloropropene (1230za), 1,3,3,3-tetrachloropropene (1230zd) and 1,1,1,3,3-pentachloropropane (240fa), or a mixture thereof, to produce a stream A comprising 1-chloro-3,3,3-trifluoropropene (1233zd), characterized in that said step i) is carried out in a low-HF liquid phase.