The Ringelmann smoke chart was used in the United States to assess smoke emissions in the early twentieth century. In fact, it may have been the most important method for measuring air pollution between the late 1800s and the environmental era. However, the popularity of the Ringelmann chart stood in stark contrast to its lack of precision, which smoke abatement experts recognized and discussed among themselves. However, the critique of the Ringelmann scale rarely left the circle of experts and never jeopardized its use. This article discusses the reasons for this striking phenomenon, pointing out that the Ringelmann chart had strong practical and symbolic advantages: it allowed smoke abatement to be conducted in a public and transparent way. With that, the history of the Ringelmann smoke chart is an instructive model for the social construction of measuring techniques.