Abstract Of the halogen plastics polyvinyl chloride, PVC, is by far the most common. Gheap and convenient it has found a multitude of applications. At some industrial fires during the last years the secondary damages have been extremely high due to the presence of PVC. Metals, concrete and electronic equipment have been destroyed by corroscon. PVC does not burn, but decomposes when exposed to fire, and in this process hydrogen chloride evolves. Together with the air humidity the hydrogen chloride forms hydrochloric acid. One kilogram of pure PVC evolves about 0.56 kilogram of hydrogen chloride, which roughly corresponds to 10 kilograms of 5 % hydrochloric acid. This amount of fairly strong acid is sufficient to cover an area of 2000 m2 with 10,000 1-mm drops per m2. It is evident that PVC fires can cause appreciable damage. The costs can be considerably decreased, however, by means of rapid and correct decontamination. The accumulation of further information is necessary for the appraisal of effective countermeasures.