In this paper we present our approach to capture and share knowledge from field studies using pattern language and hereby inform the design of ubiquitous computing. In our case, we studied frontline firefighting by observing the existing practice, by developing empathy through participation and by introducing new technology as triggering artifacts. Applying grounded theory, we distilled our findings into pattern language describing core aspects of this practice and their interaction. In a workshop, we introduced the pattern language to developers who had no previous knowledge of this practice and, in follow-up interviews, confronted them with new technology proposals for firefighters. Our study shows that pattern language, while not to be confused with an immutable description of the status quo or a direct path from contextual analysis to design, supports a reflective discussion of novel technology and the fit with and potential impact on existing practice