Information relating to the health hazards of gases and aerosols typically emitted during volcanic activity are also available from the International Volcanic Health Hazard Network (IVHHN). See introduction to volcanic gases and guidelines based on international urban and industrial pollution studies.
Freshly fallen ash grains commonly have surface coatings of soluble components (salts) and/or moisture. These components can make ash mildly corrosive and potentially conductive. The soluble coatings are derived from the interactions in an eruption column between ash particles and volcanic-gas aerosols, which may be composed of sulphuric and hydrochloric acid droplets with absorbed halide salts. The amount of available aerosols varies greatly between eruptions of similar size and volume.