Purpose: The purpose of this paper is to explore the enactment of safety routines in a transshipment port. Research on work safety and reliability has largely neglected the role of the workers' knowledge in practice in the enactment of organisational safety. The workers' lack of compliance with safety regulations represents an enduring problem that often involves first-level managers, who are willing to turn a blind eye toward divergent practices. The CHAT conceptual vocabulary and theoretical model is used to explore this issue. Design/methodology/approach: A grounded, empirical study in a large transshipment port in the Mediterranean area is conducted. Ethnographic methods including participant observation and interviews are used, and emerging data are analyzed through an interpretive methodology. The paper explores 30 employees' narrated accounts of how safety rules are enacted or infringed while living and working in the field in a transshipment port. Data obtained through organisational shadowing provided secondary data. Interview data were analyzed using content analysis, using a CHAT framework. Constant comparison and theoretical sensitivity were pursued through an iterative analysis process. Findings: This study documented the critical role the workers' knowledge played in practice in ensuring the efficient functioning of the port, and evidenced that the disconnect between safety procedures and technical productivity standards is the most important factor determining the erratic compliance with prescribed procedures. The selective application of safety norms was deliberate in nature, collectively shared and culturally regulated. Research limitations/implications: This contribution fails to address probably the most important aspect of the activity theoretical approach: its developmental orientation. The initial analysis intervention was meant to lead to a longitudinal process of expansive learning and development in the activity system. The authors had planned to initiate a cycle of expansive learning laboratories involving representatives of the dockworkers, the port management and the safety certification firm, but this had to be postponed to an undefined time due to the significant changes occurred in the international maritime cargo industry and the decision of the multinational company who owns the transshipment port to cut down its cargo traffic and privilege other ports in the Mediterranean area. Practical implications: The practical implications of the case study concern the conception and design of safety training and management for the port organisation. By acknowledging the disconnect between espoused safety routines and the constraints and affordances of the workers' everyday work practice, it is suggested that safety training could be more effective if it engaged the workers (or first-level supervisors) in the fine tuning of safety regulations. Workplace learning opportunities could enable the workers to learn and construct situated safety practices. Social implications: This paper seeks to highlight how the consideration of local knowledge and context-dependent practices can achieve better comprehension of situated application of safety norms. Originality/value: The paper contributes to understanding the complexity of enacting and translating safety procedures into everyday work practices.