Aim: To examine hospital nursing staff's working conditions in relation to infection prevention behaviours.

Methods: Data were collected through observations, interviews, and questionnaires. The participants were nursing staff and managers at surgical and orthopaedic hospital units.

Results: Nursing staff reported high self-efficacy in infection prevention behaviours, yet observational data revealed frequent lapses regardless of observed or perceived working conditions. Lapses were more frequent during interrupted tasks and when staff worked together, highlighting the influence of momentary situational factors. Lower work-related stress, greater access to structural empowerment, and stronger work engagement were found to have low but definite associations with higher levels of self-efficacy. Qualitative findings based on nursing staff perspectives showed that environmental design, workload, interruptions, knowledge, team dynamics, and leadership influenced infection prevention behaviours. Managers acknowledged these challenges and described strategies such as strengthening a supportive culture, adjusting staffing levels, and tailoring information. At the same time, they emphasised individual responsibility among staff.

Conclusions: Favourable working conditions, such as adequate staffing and access to hygiene materials, do not automatically ensure safe infection prevention work. This thesis shows that situational and emergent factors can challenge behaviours. That infection prevention lapses were more common when nursing staff worked together is a novel contribution to the field. To strengthen infection prevention, strategies must move beyond routines and address how behaviours develop in relation to clinical contexts. The findings offer important insights for healthcare staff, clinical educators, quality developers, and managers, and can inform future interventions and quality improvement work, an area of societal relevance.