Chronic diseases are the main cause of mortality in developed countries. Among them, asthma has an increasing prevalence in urban areas. We propose to use the crowd-sensing paradigm for monitoring the environment, especially the air quality parameters relevant for asthma patients. Asthma is a good candidate for participatory medicine approaches as current medical guidelines promote self-management of the disease by informed and ICT enabled patients. The paper continues our work for m-health applications for asthma patients and focuses on decentralized air quality monitoring by the patients themselves using affordable and available hardware platforms based on Arduino.