Citizen science involves members of the public collecting and analyzing scientific data using sensors. Sensors can react predictably to environmental conditions and measure aspects like air quality. A recent citizen science project involved students, scientists and public health experts using open-source air quality sensors to collect data from four neighborhoods in San Diego over a spring period. The sensors measured particulate matter and gas levels every 30 seconds, uploading averages to be viewed online. The project aimed to engage the public and gather more information on local environmental conditions.