Sensory data have always been used by concerned citizens to evaluate environmental variables within volunteer monitoring initiatives. The work presented in this paper intends to explore the possibility of using human sensory data as a source of information to monitor environmental quality variables within a public participation context. A case study that uses untrained citizens to monitor chlorine flavour of tap water is presented. Two collaborative monitoring tests were developed: (1) the one-sample one-trial test and (2) the Chlorine@Home test. The tests intended to address the participatory context required by collaborative monitoring initiatives. The development of the collaborative tests was supported by two tests that were designed for a laboratory context and explored sensory methodologies. The sensory tests implemented were: (1) the paired comparison test, (2) the forced-choice triangle test (ASTM Method E679-04). The collaborative experiments showed that the ability to detect chlorine flavours on a participatory context was independent on chlorine concentrations. The use of sensors by citizens may be a way to increase the credibility of the information. Nevertheless, this case study suggested that more research should be carried out to explore ways to involve citizens while increasing data reliability.