Exposure to air pollution is affected by human behaviour, and has consequences for individual and collective health. One way to lessen the health effects of air pollution is to change personal travel behaviour with the help of new information, communication and sensing technologies. Our social research tracked the experiences of participants, air quality and technology enthusiasts, based in London who financially contributed to participate in an early-stage technical trial of a new air pollution sensor and app providing individuals with air pollution information (specifically levels of NO2 and VOCs). This paper reports the results of a before and after survey (returning respondents n = 22) and 12 in-depth interviews with individuals who took part in the beta test of the sensor and phone app. The survey results show that travel-related behaviours and attitudes relevant to air pollution did not change after using the technology. In contrast, expectations of technology performance and the extent it would influence behaviours were significantly lower after the trial than before. Further exploration during semi-structured interviews found that the participants, given their already high level of engagement with the topic, felt the capacity for immediate individual behaviour change was limited. As well as time and practical constraints, most people in this sample felt they were already doing what they could to avoid high levels of air pollution in their daily lives. Despite this, they had some recommendations to improve the app, such as the inclusion of real-time and historic maps, and the ability to make self and other comparisons. Overwhelmingly, people saw a broader role for the technology to engage the public with air pollution through raising awareness, and harnessing citizen science to collect diverse reliable data to inform policy and influence local policymakers to reduce air pollution levels.