Volcanoes release tephra, gases and aerosols into the atmosphere during both eruptive and quiescent activity. Volcanic degassing exerts a dominant role in forcing the style and timing of volcanic eruptions. Emissions range from silent exhalation through soils to astonishing eruptive clouds injecting tephra, aerosols and gas into the atmosphere. Strong explosive eruptions pose critical hazards on the ground and in the air and represent one of the most important natural driver of climate variability at annual-multidecadal timescales. Persistent quiescent degassing and low-magnitude eruptions, on the other hand, may impact on regional climate system. Through direct exposure and indirect effects, volcanic emissions may destroy the natural and built environment, influence local-to-regional air quality and seriously affect the biosphere and environment and, in turn, livelihoods causing socio-economic challenges. Tephra, aerosols and gas emissions are observed and monitored via a range of in situ direct and remote sensing techniques to gain insights into both the subterranean-surface processes and quantify the extent of their impacts. Inverted data are then used to tune models of subsurface and atmospheric/climatic processes as well as laboratory experiments and to validate and interpret satellite observations. This session focuses on the state-of-the-art and interdisciplinary science concerning all aspects of volcanic tephra, aerosols and gas emissions and their impacts on societies, the environment and climate. We invite contributions on all aspects of volcanic plumes science, their observation, modelling and impacts. We welcome contributions that address hazard assessment and impacts from volcanic degassing both in crises and at persistently degassing volcanoes. This session is organized under the auspices of the IAVCEI Commission on Tephra Hazard Modeling.