The emissions of various types of greenhouse gases (GHGs) from natural and industrial sources are undergoing a great deal of scrutiny around the world. The three main GHGs that are of most concern are carbon dioxide (CO[subscript 2]), nitrous oxide (N[subscript 2]O) and methane (CH[subscript 4]). CO[subscript 2], N[subscript 2]O and CH[subscript 4] are all efficient absorbers and emitters of thermal infrared radiation, and as a result, once they are emitted into the atmosphere, they can contribute directly to the greenhouse effect. One of the most popular GHG measurement techniques is near dispersive infrared (NDIR) gas analysis. This paper describes a high school Physics or general science practical exercise that uses an inexpensive NDIR based gas analysis unit combined with a gas capture hood to measure CO[subscript 2] gas flux from different water types and soil/fertiliser combinations. From this, students will gain an understanding of how GHGs are emitted from natural sources and how they are measured by scientists.