This is a paper concerned with security, surveillance and notions of atmosphere and ambience. Whilst surveillance and security research has been excellent at examining socio-spatial relations drawn into the production and consumption of surveillance technologies, systems and practices, it has been far less well attuned to the material-affective relations, presences and absences it comes to constitute as the fabric of public space. Research within human geography and a broader 'new materialism' within the humanities and social sciences has become increasingly interested in exploring affective atmospheres, yet largely ignorant of a well established school of thought within French urban and social theory of 'ambiance'. This paper explores the providence of considering atmospheres and ambiances for the examination of surveillance through the case study of two major railway stations in Britain and France. The paper proffers some methods and techniques for the further exploration of atmospheres/ambiances of security.