This paper reports on a particular aspect of a larger ethnographic study of nursing culture in an intensive therapy unit (ITU), accomplished through participant observation over a 12‐month period, followed by interviews with 15 nurses. The paper suggests that the ITU environment is perceived as ‘dangerous’, its dangerousness stemming from the ambiguity of its patients’ conditions. Drawing on anthropological concepts of liminality, pollution, anomaly and breaching of boundaries, the paper identifies various ambiguities inherent in ITU patients’ conditions. It then explores (...) the ways in which these anomalies are managed through sequestration and other ritual and symbolic practices. Notwithstanding the undoubted scientific reasons for particular nursing practices, the paper argues that there are also ritual and symbolic elements serving other more complex purposes, both protecting patients and staff and symbolising the highly valued phenomenon of keeping patients safe. The paper identifies a contradiction inherent in nursing work in this locale inasmuch as rituals and symbolism coexist with technical and research‐based elements of nursing care. (shrink)