There is provided a biogas flux chamber constructed in one embodiment from a metal can with an open bottom and an epoxy interior coating. The chamber is inserted into the soil to allow influx of soil gases. The lid includes a sampling septum and a vent tube to prevent pressure build-up when the lid is in place which allows for an increase in interior gas concentrations. The rubber sampling septum is installed in a hole in the lid. The vent tube is constructed using flexible copper tubing inserted through the lid and secured using a bulkhead-fitting, and rubber O-ring to seal the insertion hole. The copper tubing is bent to form a double-curved ‘C’ shape which positions the open ends of the tube above and below the lid surfaces.