Abstract: Phosgene is produced by reacting chlorine and an excess of carbon monoxide in the presence of activated charcoal in a two stage process. In the first stage, the chlorine and carbon monoxide are reacted in a tubular reactor containing activated charcoal at a temperature above 250.degree. C. until 95 to 98% chlorine has reacted. The reaction gases are cooled to a temperature of from 50.degree. to 120.degree. C. and then introduced into a second reactor maintained at 50 to 100.degree. C. where the phosgene-forming reaction is completed. The phosgene leaving the second reactor has a residual chlorine content of less than 50 ppm. The heat generated during phosgene formation is used to produce steam.