Fumarole, << FYOO muh rohl, >> is a hole or vent in the ground that gives off volcanic gases. Most fumaroles occur in inactive volcanic regions, such as Yellowstone National Park. The gases given off are mainly steam mixed with small amounts of carbon dioxide, hydrogen, hydrogen sulfide, hydrogen chloride, hydrogen fluoride, and sulfuric acid. Some of these gases are poisonous. Others may irritate the throat and lungs and cause choking. Fumaroles that give off sulfurous gases are called solfataras. See also Hot springs .
