Lake Nyos and the CO2 danger

Invisible volcanic gas can also be dangerous. On August 21, 1986, a large amount of accumulated carbon dioxide was suddenly released from Cameroon’s Lake Nyos. The dense cloud flowed down valleys, displaced breathable air, and fatally asphyxiated people and animals in nearby settlements. Carbon dioxide is heavier than air and can pool in poorly ventilated low areas, although its behavior outdoors depends on terrain and weather.