In the period up to 2020, European chlor-alkali plants using mercury technology will be progressively shut down and partially replaced by plants using membrane technology. As a result, several thousand tonnes of mercury currently in use in the plants will be redundant and will have to be dealt with in an environmentally satisfactory way. Some years ago, the Euro Chlor members committed to sell the mercury recovered form shut down plant to the mine of Almadén to replace fresh mined mercury (emissions). In the frame of the new EU Regulation proposed to ban the export of mercury from Europe (Ref 1), Euro Chlor has published an agreement that was accepted by the European Commission for permanent storage of the redundant mercury in the metallic form (see Ref. 2). This guideline refers to this permanent storage of metallic mercury. It aims to give chlor-alkali producers practical advice on recovery, transport and storage that will help them to comply with the Regulation and with established good practice.