Safety and risk assessment and management involve, among other, anticipating, preventing, and planning for technological decline, which may come in the form of ageing and disuse of a technological system, or its coordinated phase-out. In the interdisciplinary literature on sustainability transitions, coordinated phase-out is typically the centre of interest. Technological decline may be understood as the process of diminishing production and/or use of a given technology. Using three empirical examples, the chapter illustrates and identifies two types of decline: weak and strong. Weak decline involves reversible decline and lower costs of re-emergence, whereas strong decline signifies high irreversibility. The chapter concludes with practical recommendations for risk assessment and safety management, emphasizing the need for strategic mapping of technologies and coordinated efforts from various stakeholders.