Spectacle computing is a novel strategy for vibrantly projecting information into the public sphere using expressive and tangible media. We demonstrate an example of this computing meme with large, glowing balloons that change color based on input from attached air quality sensors (exhaust, diesel, or volatile organic compounds). In two public installations (city street and public park) and a deployment with six everyday citizens, we invited stakeholders to playfully explore and actively participate in visualizing surrounding air quality. We also created a do-it-yourself (DIY) kit that includes a printed circuit board, electronic parts and instructions for building the air quality balloons. In a workshop, six non-expert users successfully assembled functional balloons, validating our technology as a DIY tool for public air quality visualization. Our deployments and workshop highlight play and spectacle as essential elements for public participation and activism. We outline design guidelines for future spectacle computing projects that engage stakeholders with environmental data and empower them to transform urban landscapes.