Final year nursing students and infection prevention and control nurses were recorded verbalising their hand hygiene decision-making while working through clinical scenarios on a computer, to understand what factors they were taking into account in choosing a decontamination method (hand washing or alcohol based hand rub/gel) or to wear gloves. Results demonstrated an overuse of gloves, and underuse of gel. Three main themes emerged: 'Experience or expectation'; this was what they had seen on placement, or it was what 'we' do. 'Just in case,' was characterised by an awareness that what they would do wasn't actually necessary but they tended to do it anyway. Thirdly, 'gel doesn't feel clean,' was characterised by a feeling that using gel didn't make the nurses feel clean after 'dirty' tasks, even though gel is actually more effective. There was little evidence that participants were making risk assessments based on the individual patient characteristics given, or the tasks, as they had been taught to do. Choice of hand decontamination agent and whether to use gloves appeared to be based on an habitual characterisation of whether the task was 'clean' or 'dirty,' with a very low threshold for 'dirty' based on an excessive perception of risk to the student.