Safe operations are critically reliant on the practices and expertise of companies and their personnel. Their importance has been highlighted throughout accident analyses where warnings have been shown to go ignored, and the scale of what could go wrong misjudged. A common view of learning in professional fields has been one of knowledge ‘transmission’ through training courses and seminars. This article draws attention to the more informal and experiential means by which knowledge is acquired. Grounded in the literature on high reliability theory, organisational learning and naturalistic decision making, this ethnographic research examines the learning experiences of ‘young’ engineers in the Australian gas pipeline industry. The particular focus is on young engineers’ appreciations of safety and their role in its continuation. It argues that, in addition to formal knowledge delivery, young engineers and their colleagues are relying on informal mentoring and experience in their acquisition of safety knowledge and professional expertise more broadly. The article is based on qualitative interviews with 34 gas pipeline engineers including new people to the industry, their managers, and technical experts. The work is investigative rather than hypothesis-testing. It concludes with some areas in which further work would be valuable, including an evaluation of the extent to which informal learning methods are appropriate in a hazardous industry context, and the formal organisational features that might effectively support them.