The copper-chlorine cycle of thermochemical water splitting, using various heat sources, is a promising technology for hydrogen production. The chemical hazards accompanying the new technology affect significantly the industrialization of the cycle, but have scarcely been examined. This paper addresses this need by examining the copper(I) chloride (CuCl) hazards that may be generated in the cycle. Regardless of the variations of Cu-Cl cycle, copper(I) chloride is always present, serving as an intermediate compound that may cause health concerns. In this paper, the CuCl hazards are quantified for each process from the generation source of the hazards along with the paths where the CuCl may be present. The processes of greatest relevance include oxygen production, heat recovery, solidification, and dissolution. The options for reducing the CuCl hazards in a Cu-Cl thermochemical hydrogen production plant are evaluated from the perspectives of variations of the Cu-Cl cycle, process integration, heat recovery, and equipment design. It is concluded that using the intake reactant Cu2OCl2 for the oxygen production step to absorb CuCl vapor is the most preferable option compared with other alternatives such as absorbing CuCl vapor with water or CuCl2, building additional structures inside the oxygen production reactor, and cooling the exiting gas at the outlet of the oxygen reactor. Crown Copyright (C) 2012 Published by Elsevier B.V. All rights reserved.