With the increased global focus on the environment, pollution, greenhouse gases, as well as carbon footprint, a multitude of initiatives have emerged in order to reduce air pollution and also increase awareness of air quality. In this paper, we developed CyclAir, a system enabling cyclists to monitor the traffic-related air pollution, measured in carbon dioxide (CO$_2$2) levels, both in real-time as well as retrospectively. Based on a first user study with seven test participants, we found that our participants were often confirmed about their preconceptions of the immediate CO$_2$2 level and air quality, but interestingly they were also sometimes surprised. 6 out of the 7 participants expressed willingness to change route choosing behavior when presented with new evidence about the air quality, even when this increased the route length.