An original and important research programme was developped in order to assess out the efficiency of thE geocomposite Somtube for the drainage of gas. In the first part, laboratory experiments, based on transmissivity tests, wen performed on the non-woven layer and the incorporated pipes. They show how air transmissivity tests can be correlated tc water transmissivity tests. In the second part, full scale tests, with this geocomposite, were perfom1ed in a 10 m x 2 m x 0.8: m box : air flow is injected below a soil layer, penetrates the geocomposite and is drained by the non-woven layer and thE small pipes. Air pressures in the non-woven layer and in the pipes arc measured as a function of the air discharge Comparisons between experimental results, theoretical model and correlations between air ilow and water flow an presented.