Good to Know is a new feature that allows members of the community to answer questions from WebMD experts, doctors, staff, and other community members. We're testing this new feature and we'd like your feedback.
the cylinder (known as Bottom Dead Centre or BDC) the exhaust valve starts to open. As the piston now moves up the cylinder, the hot gases (consisting mostly of nitrogen, carbon dioxide, water vapour and unused oxygen) are expelled from the cylinder. As the Piston approaches TDC again the inlet valve starts to open and the cycle repeats itself.
Volcanic gases are probably the least showy part of a volcanic eruption, but they can be one of an eruption's most deadly effects. Most of the gas released in an eruption is water vapor (H 2 O), and relatively harmless, but volcanoes also produce carbon dioxide (CO 2), sulfur dioxide (SO 2), hydrogen sulfide (H 2 S), fluorine gas (F 2), hydrogen fluoride (HF), and other gases. All of these gases can be hazardous - even deadly - in the right conditions.