[citation needed] The event resulted in the supersaturated deep water rapidly mixing with the upper layers of the lake, where the reduced pressure allowed the stored CO2 to effervesce out of solution.

[16] Since carbon dioxide is 1.5 times the density of air, the cloud hugged the ground and moved down the valleys, where there were various villages.

For roughly 23 kilometres (14 mi), the gas cloud was concentrated enough to suffocate many people in their sleep in the villages of Nyos, Kam, Cha, and Subum.

[4] About 4,000 inhabitants fled the area, and many of these developed respiratory problems, lesions, and paralysis as a result of the gas cloud.

[17] It is a possibility that other volcanic gases were released along with the CO2, as some survivors reported a smell of gunpowder or rotten eggs, which indicates that sulfur dioxide and hydrogen sulfide were present at concentrations above their odour thresholds.

I got my motorcycle ... A friend whose father had died left with me (for) Wum ... As I rode ... through Nyos I didn't see any sign of any living thing ... (When I got to Wum), I was unable to walk, even to talk ... my body was completely weak.Following the eruption, many survivors were treated at the main hospital in Yaoundé, the country's capital.

Poisoning by these gases would lead to burning pains in the eyes and nose, coughing and signs of asphyxiation similar to being strangled.

[9] Interviews with survivors and pathologic studies indicated that victims rapidly lost consciousness and that death was caused by CO2 asphyxiation.

[20] At nonlethal levels, CO2 can produce sensory hallucinations, such that many people exposed to CO2 report the odor of sulfuric compounds when none are present.

[24] Starting from 1995, feasibility studies were successfully conducted, and the first permanent degassing tube was installed at Lake Nyos in 2001.

The 2020 study found that when these errors were accounted for, the risk of a gas eruption at Lake Kivu did not seem to be increasing over time.