process and apparatus for extracting soil gases from the earth and analyzing the collected gasses to determine the presence in the soil of gases produced by lower subterranean hydrocarbon deposits , such as petroleum and methane gas . the soil gases are passed from the soil through a soil probe and conductive tubing into a gas collector and concentrator comprising at least one molecular sieve which is chosen and selected for its ability to trap the gas or gases of interest . when the collection and concentration process is completed the gas collector is removed from the field apparatus and taken to a laboratory where the molecular sieves are heated to release the trapped gases . the gases are then analyzed in a gas chromatograph .