OpenAQ is the largest, open source air quality data platform, hosting 5+ billion real-time and historical measurements from 120 countries, and serving an average of 35 million API requests per month. The data have been used for a wide variety of applications, from air quality forecasts produced by NASA scientists to platforms communicating air quality in India to data-driven media reports by the general public. By providing this foundational data infrastructure, OpenAQ is able to convene people and organizations from across the globe to further raise awareness and develop innovative solutions to combat air pollution. The talk will give a technical overview of the platform, highlight the impact through user stories, and feature new tools developed with the community to enhance the platform and effectively use the data to fight for clean air. Air pollution, responsible for one out of eight deaths around the world, is a global environmental and public health crisis. Despite the urgency of this growing problem, only 50% of governments worldwide produce air quality data, leaving 1.4 billion citizens without access to fundamental information that could protect them from the harmful effects of air pollution. Where data does exist, data are often in inconsistent and temporary data sharing formats, making it difficult for the public to readily access and make use of the data. The OpenAQ platform aggregates and harmonizes real-time and historical air quality data from 120 countries from a variety of sources including reference-grade government monitors to community-led low-cost sensors to research-grade data. The open source platform hosts 5+ billion data points and the open API serves an average of 35 million requests per month. The data has been used for a wide variety of applications, from air quality forecasts produced by NASA scientists, to platforms communicating air quality in India, to data-driven media reports. By filling a basic data-access gap and building foundational open source tools, OpenAQ has empowered diverse individuals, organisations, and sectors across the globe to fight for clean air. How has opening up air quality data transformed the way we think about air pollution? What kinds of innovative solutions have been developed? Looking into the future, how do we address data accessibility, coverage, and transparency in order to most effectively enable cross-sector and cross-cultural collaboration to drive action? This presentation will give an overview of the platform, highlight impact stories among the OpenAQ Community, and share new tools we have developed with communities to share insights into how open air quality data has shaped and continues to shape the global fight against air pollution.