He told a news conference that a long pipe was inserted 210 metres (690 feet) into Lake Nyos.
More than 1,700 people died after deadly gases spewed from Lake Nyos 15 years ago.
Scientists from the United States, France and Cameroon are using a series of giant pipes to release carbon dioxide from deep down in the waters of the lake.
They say that pressure from the gas has built up again and a similar tragedy could happen at any time.
In August 1986, the lake released a cloud of carbon dioxide which hugged the ground and flowed down surrounding valleys to suffocate thousands of local villagers and animals.
The rare phenomenon also occurred at Lake Monoun in the same volcanic zone two years earlier killing 34 people.
According to some reports, the lake now contains twice as much carbon dioxide as was released during the explosion. Earlier attempts to siphon off the gas had to be abandoned for financial reasons.
Autosiphon project
The process termed autosiphon was tested for the first time in 1995 by French geochemist Michel Halbwachs.
He told a news conference that a long pipe was inserted 210 metres (690 feet) into Lake Nyos.
"The very long pipe spews 90% carbon dioxide and 10% water to a height of 50 metres," he said.
The Nyos Organ project, as it is known, involves inserting 12 pipes into the lake.
"By doing so, the accumulated carbon dioxide in the depths of the lake will be gradually released at very high altitude in the atmosphere and will not be dangerous to people living nearby," he said.
The project will be monitored by satellite. Cameroon's minister for scientific and technical research, Henri Hogbe Nlend, said the project would cost about $2.8m.
He said that the US Government had already contributed $450,000.