We describe our research--its approach, results and products--on Danish emergency medical service (EMS) field or "pre-hospital" work in minor and major incidents. We discuss how commitments to participatory design and attention to the qualitative differences between minor and major incidents address challenges identified by disaster sociologists when designing for major incidents. Through qualitative research and participatory design, we have examined the features of EMS work and technology use in different emergency situations from the perspective of multiple actors. We conceptualize victims in incidents--and particularly in major incidents, where on-site medical assessments is highly incomplete--as boundary objects over which the complex and imperfect work of coordination is done. As an outcome of our participatory design approach, we describe a set of designs in support of future EMS work. Author Keywords Emergency medical service (EMS), major incidents, minor incidents, ...