Some gases, such as carbon dioxide, contribute to global warming, while others, like sulfur dioxide, can cause global cooling and ozone destruction. Studies of volcanic emissions will allow scientists to compare volcanic gas output to emissions from man-made sources and to assess the effects of both past and future eruptions on Earth's climate. Yes, volcanic gas can be harmful to humans, animals, plants, agricultural crops, and property. Usually, the hazards from volcanic gases are restricted to the areas immediately surrounding volcanic vents and fumaroles and to low spots on the flanks of volcanoes. But these hazards can sometimes persist for long distances downwind from a volcano.
Health hazards can range from minor to life threatening.
Exposure to acid gases such as sulfur dioxide, hydrogen sulfide, and hydrochloric acid can damage eyes and mucous membranes along with the respiratory system and, under extreme conditions, can lead to death. The toxicity of carbon monoxide is well known, although it is rarely abundant enough to cause serious problems. One of the most serious hazards occurs when volcanoes emit large quantities of carbon dioxide. Carbon dioxide is heavier than air and collects in low spots, displacing air in these locations. Hundreds of people have died of carbon dioxide asphyxiation near volcanoes in the past two decades, most of them in Cameroon, Africa, and in Indonesia.