Lava flows from eruptions on Reykjanes peninsula in Iceland started burning urban structures on 14 January 2024. Volcanic emissions and urban fires, respectively, are known to contain many chemical compounds that are hazardous to health. While these distinct end member compositions are better known, lava-urban interface (LUI) emissions have not been studied. Key hypotheses: LUI emissions have unique chemistry due to the combination of volcanic and human-made compounds. The interaction impacts the combustion process, the composition of the emissions released into the environment, and the chemical reaction pathways in the atmospheric plume. The LUI interaction may also be modifying the degassing processes in the lava, and release of magmatic volatiles. Eruptions at the urban interface lead to higher human exposures than remote eruptions because of their proximity to communities; and small eruptions can cause severe air pollution in populated areas. Lava encounters urban space quasi-periodically, for example Kilauea, Hawaii 2018, Cumbre Vieja, La Palma 2021 and now on Reykjanes, Iceland (2024 - present). Despite the recognition of the importance of characterising chemistry of air pollution sources, LUI emissions remain unstudied, likely due to a combination of challenging sampling conditions, and the unpredictability and the short duration of each eruptive episode. Globally, the number of people exposed to LUI emissions is growing because of building expansion into previously uninhabited areas. For instance, the homes burned by lava in Iceland in January 2024 were newbuilds, the construction of which began when the volcanic system was already in unrest. We will use the ongoing activity in Iceland as a natural laboratory for the first ever characterisation of LUI emission chemistry at-source and in the near-field (1-40 km distance).