Abstract The catalyst of the ITER Vent Detritiation System (VDS) has to oxidise the tritiated gases: the resulting tritiated water is trapped in order to provide the tritium confinement function of the VDS. An experimental study has been carried out in order to determine the VDS catalyst ability to operate when exposed to the products of combustion released during a fire. In our tests the VDS catalytic recombiner has been tested in the presence of fumes generated by the combustion of selected materials (polyvinyl chloride, methyl methacrylate, vacuum pump oil and polytetrafluoroethylene). These materials have been burnt in an oven at 200 °C: the arising combustion fumes have been sent into a catalytic bed where a Pt 0.5% on alumina catalyst operated the conversion of the tritiated gases into tritiated water at 400 °C with a spatial velocity of 6000 h −1. The catalyst efficiency has been assessed by adding tritium as a tracer to the combustion fumes entering the catalytic recombiner and measuring the activity of the tritiated water collected after this reactor. The studied catalyst has been mainly affected by the fumes coming from the combustion of polyvinyl chloride: the measured catalyst efficiency has been 86.7%. Especially, in this case the presence of chlorides would have impaired the detritiation process by poisoning the catalyst. The combustion tests with methyl methacrylate and vacuum pump oil with polytetrafluoroethylene have shown slither reduced catalyst efficiencies of 91.1 and 93.5, respectively.