Method for making isocyanates

Producing diisocyanate comprises reacting corresponding diamines with stoichiometric excess of phosgene in at least a reaction zone, where: the reaction condition is selected in such a way that at least the reaction components diamine, diisocyanate and phosgene are in gasiform at these conditions; and the reaction zone is loaded with a diamine- and a phosgene containing gas stream; the chlorine portion in the phosgene stream before the mixing with the amine containing stream is less than 1000 wt.ppm and/or the bromine fraction in the phosgene containing stream is less than 50 wt.ppm. Independent claims are included for: (1) use of phosgene with a content of molecular chlorine of less than 1000 wt.ppm in a gas phase phosgenation; and (2) use of phosgene with a content of molecular bromine of less than 50 wt.ppm in a gas phase phosgenation.