Vog is the linguistic contraction of volcano and fog and you'll find it in Hawaii. The chemistry involves SO2, water vapor, and sunlight. When vog at its worst on the rim of Kilauea's crater, the Volcano National Park can be shut down due to health concerns. (Sulfuric acid droplets are not good to inhale at high concentrations.) Vog concentrations and visibility reduction depend on many factors, including the volcano's level of emission, the strength and direction of the prevailing winds, and also the strength and height of the trade wind inversion (a warm, stable layer in the lower atmosphere that traps aerosols close to the ground.) The image below was taken by the Space Shuttle, the gray areas show the vog.