Early warning consists of monitoring precursors of a potential hazard to understand if it is evolving to a real risk and then be able to orchestrate an early response before the event happens in order to reduce its impact and damages. It mainly consists on collecting updated and reliable data that can help emergency operators to understand how a situation is evolving and project its consequences, that is, to support situation awareness on a potential risk. This process could be improved by

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... rating volunteers and citizens into the data collection process given that they are intelligent sensors equipped with mobile devices that can be used almost everywhere to collect and share information. In this paper we introduce a system relying upon ubiquitous computing to integrate citizens in checking the evolution of potential hazards. An asynchronous focus group technique to assess the system with EM professionals is also described in the paper.